The Iron Keep can be reached by changing paths with Licia in the Cathedral of Majula, traveling through Huntsman's Copse, Harvest Valley and Earthen Peak. After defeating the second boss of Earthen Peak (Mytha, the baneful queen), head through the path at the other side of her boss room, travel up the lift and follow the short path to the start of the Iron Keep area. Down the staircase to the left is the first bonfire of the area and where we will start off. Next to the first bonfire of the area, you will encounter magma for the first time. This substance can be passed through, but only if you have significant fire defense (at least over 1000+ to retrieve all items and return to safety).
Players with the flame sweat spell, decent fire resist equipment, the flame quartz ring and small orange burrs are all ways you can raise it to this level. Life Gem or regeneration items can also be used to offset the damage taken when moving through magma. There are also water jars in this level that cover the player in water and will provide some protection until the water is evaporated by the heat (a pharro's device in this area can also provide this effect). I will mention these paths, but keep that information in mind when attempting to reach the items on those paths. The short magma path next to the bonfire leads to a Human Effigy which is found under the stairs.
Head back up the stairs and cross over the bridge. Halfway across, you should see a chunk missing, look down below for another magma path that leads to a Bonfire Ascetic on a corpse. Only try and reach it if you meet the requirements stated above. On the other side you will encounter two new enemies of a type not seen before. These knights wield katanas, and unlike most knights so far in the game are quite fast and lethal. They cover distance fast, attack rapidly and have a decent amount of health. Their attacks are easy to learn (a lunge and a slash) but due to their speed, can be difficult to avoid. The first knight on the right will be hiding behind the pillar on the right at the end of the bridge, the left knight will be leaning against the wall to the left of the stairs leading into the keep. Try and only lure one at a time if you can. Ranged characters should be able to kill the knights off before they reach them, but melee characters will need to learn their attack patterns and when to block before they can defeat them easily.
After dealing with the first pair of knights, open up the large metal door to head inside. A flaming bull statue will be spouting flame directly ahead, with a katana knight to the left of it. If you move to the right and look behind the pillar on the right side of the room, you should spot a second katana knight. A third katana knight is up the stairs on the far side of the room (only triggered by being to close when attacking the second katana knight, otherwise it will remain at the top of the stairs). If you are a ranged character, take care of the second knight first (staying nearly in line with the pillar to prevent luring the third). The first knight will ignore you until you go up the staircase on the left or attack him directly. This should allow you to take out the second knight easily and then turn your attention to the now alone first knight. Finish him off to clear the room (you can climb the stairs on the far side of the room and kill the third knight as well to make life easier later if you want).
In front of the flaming bull statue, you should spot a corpse with an item on it. This item is the Iron Key which is important in opening a few new paths for you to travel. Some people say that you can safely retrieve it by inching towards it on the left side of the stream of fire. Personally I just grabbed it, died and recovered my souls. There is also a safer way to retrieve it which requires you to use the water vases in a nearby room. If you wan't to use this method keep following the guide and I will mention it when we reach the vases. Now, head back down the small set of stairs to the entrance of this room and head through the door to your right (not up the staircase where the third knight was). This will take you to a short hallway with a set of stairs leading up to your left and a small circular room directly ahead. In the small circular room you will meet Magerold, who will sell you some useful items (including a branch of yore) as well as a selection of spells. When you are ready to move on, head back to the set of stairs you just went past in the hallway.
At the top of the stairs is another katana knight, back out into the fire bull statue room if you need the space to deal with him. In the room at the top of the stairs you should find a corpse with a Pharro's Lockstone to retrieve on a ledge overlooking the fire bull statue room. The jars in this room contains water vases that you can use to retrieve the iron key more safely from the flaming bull statue below. Smash a vase to cover yourself in water, drop back into the room and grab the key from the fire stream. Back in the room we were just in, you should be able to find a hidden wall immediately to the right as you stand at the top of the stairs.
Head through the small room to reach a slightly larger room with a ballista inside, as well as a corpse holding some fire arrows. The wall the ballista is pointing towards is also an illusion and opens up into another larger room with a greatbow knight on a ledge with his back to you and two katana knights (one if you killed the third knight in the flaming bull statue room as this room connects with the top of the stairs in that room). You can use the ballista to attack the greatbow knight, but this is generally less effective then getting in a few direct attacks before he can react (back stabs especially). Be careful killing him as you may accidentally lure both katana knights further in the room (which can easily lead to death).
Lure the katana knights one by one to finish them off. The left hand stairs here lead back down to the flaming bull statue room while the right path leads to a huge open area with a raised drawbridge and a large machine at the back of the area. This is a giant furnace that we will need to travel through shortly (don't worry, it will be off at the time) but first we need to clear the path and lower that bridge. Melee characters will probably want to equip or invest in a ranged weapon here to lure enemies. On a ledge up and to the right you will see a Greatbow knight as you follow the path (on the right wall when entering this area). Ranged characters will want to take care of this nuisance to prevent the constant stream of arrows when exploring this area.
You will also see a katana knight standing on the raised bridge. Ranged characters will be able to lure and attack him to take care of him early. Follow the path along the left wall of the room to meet another katana knight. After defeating him, look to the far wall ahead to see two knights. The larger one on the upper level is a knight captain. They are stronger than regular katana knights and can imbue their weapons with lightning. There will also be another greatbow knight on the ledge below him. Take out the greatbow knight with ranged attacks if you can (the captain won't bat an eye) and then hit the captain. The captain will drop down when attacked so be ready if you are just luring him down. There is also another captain across the gap to the right that you can take out early with ranged attacks.
Turn around to see a set of stairs leading down on your left to the furnace I was talking about earlier. Nearby (looking from partway down the stairs) is another katana knight hiding under the walkway. Once he is taken care of, pull the lever here (but make sure that furnace door stays closed or else you will be burnt to a crisp). This lever lowers the closer end of the bridge in the center of the area, allowing you to cross it. Head back upstairs and onto the newly lowered bridge. On the far side, a greatbow knight will start firing from the left side (next to the mist door) so use the pillar at the far end of the bridge to block the arrows as you fire back or drop off the end of the bridge and attack in melee. The mist door here leads to the first boss of the area but we can still pick up a few items here and lower the bridge further to return to the bonfire and stock up for the boss fight.
Look in the opposite direction from the mist door to see a chest. You can jump across the gap in the walkway to reach it and pick up the Zweihander inside. Head back to the gap in the walkway and look towards the lava below to see a set of metal stairs you can jump to. These stairs have a corpse holding a Dull Ember on them (used to allow the blacksmith McDuff to imbue your equipment with elemental and other stones, return it to him and he will perform this service). Head into the room and use the ladder inside to reach the upper area. A pharro's device can be found in the wall here that generates water to cover yourself with (used to access the magma path in this area). After deciding to use it or not, drop down onto the ledge where we just found the zweihander and jump across the gap towards the mist door.
You may have already noticed that the pillars to the left of this walkway have large ledges around them. Jump onto the one closest to the mist door (you should be able to see the corpse on it) by angling your jump towards the pillar itself. This way you should roll into the pillar, not off and into the lava. Pick up the Large Soul of a Nameless Soldier and Red Leech Troches from the body. Below you will be a platform with a lever on it that you can drop down to and pull. This should drop down the bridge so that it is level, allowing passage both ways. This will allow you to stock up at the bonfire before the boss fight when we get back up to that area.
Don't open the large metal door (furnace... burn .... crisp.... yada yada). If you look down from this platform you should see a set of metal stairs below that you can drop down to. Following these stairs down leads to a magma path with a Phoenix Parma Shield in a chest at the end. Make sure to only attempt this if you are prepared with the fire resist strategies from earlier. To move on, head up the stairs and turn the wheel here on the metal door to deactivate the furnace. This makes the previous furnace doors safe as you can now pass into the furnace itself. To do this, move along the ledge to the right and drop back down to where the lever you just used was.
Enter the furnace door and grab the Petrified Dragon Bone and Large Titanite Shard from the body inside. Climb the ladders to meet nothing (or the captain you didn't kill before if you have no ranged attacks). Deal with the captain if he is there and grab the Green Blossom and Radiant Life Gem from the corpse next to the ladder at the end. Climb up the ladder and you should have a door directly in front of you with a bridge inside with enemies at the other end. Leave that for now as we will be coming back here after the boss fight (it's a quicker trip back if something goes wrong). For now, take a left from the top of the ladder and confront the captain if you didn't kill him earlier with ranged attacks.
Drop down to the platform below (engaging the greatbow knight if you didn't kill him before) and open the chest. Inside is a Life Ring +1 and a Twinkling Titanite to collect. Next to the chest is a ladder that leads down to a walkway just above the lava. At the far end is a body with the Soul of a Proud Knight and a Repair Powder on it. Climb back up the ladder and drop down to the main walkway. Now is a good time to return to the bonfire and stock up before entering the mist door on the far end of the bridge. When you are ready, enter the mist door to confront the first boss of the area.
Boss: Smelter Demon
Personal Death Count: 60+
Lunge: He can perform a stab attack (a straight lunge) which is very quick in comparison to his other attacks. The lunge (due to it's speed) can take players by surprise so always expect this one as it is harder to avoid most of his attacks. To avoid the lunge, roll to the side.
Overhead Smash: The smelter demon raises both hands and his sword overhead slowly and then slams it into the ground towards the player. There is a slight delay before he actually moves the sword and he can reposition it if the player dodges too early. Be very wary of dodging early as it will likely hit you. When he has lit the sword on fire, it also adds a flaming wave that is released from the tip of the sword, shooting away from him (making rolling backwards impossible. Roll to the side to avoid this attack.. The long recovery time allows a safe heal or attack.
Reverse Slice: The smelter demon will bring his sword all the way across himself to the other side quickly and then slash horizontally twice (the first slice being a backhand and the second traveling in the other direction. Roll backwards out of range or time your sideways dodge perfectly to avoid taking damage.
Slice: The smelter demon will bring his sword arm back all the way behind him quickly and then slash horizontally twice (returning from the other side after the first swing). He can stop the combo here or continue it with one of two attacks. After this he can perform a stab attack (a straight lunge) or leap into the air for a drop attack. The lunge (due to it's speed) can take players by surprise so always expect this one as it is harder to avoid than the jump attack. To avoid the lunge, roll to the side. It will have additional linear flames shoot out if he has lit his sword as well. The jump attack can be backed away from to avoid or rolled away from backwards. If you are too close slightly after he performs the attack he will detonate an AoE around himself. Canny players can actually purposely trigger this AoE to keep him stationary for another attack or two but it is a risky strategy.
The Smelter Demon is an optional boss (he can be bypassed by traveling through the deactivated furnace in the prior room to reach the upper levels past his room). Players who are struggling against this boss can come back later with better equipment and / or stats and challenge him again. The smelter demon may not seem like a difficult boss initially (he takes acceptable damage from hits and most of his attacks are relatively easy to dodge (although some are a real nuisance). But he has several nasty tricks that will kill you over and over again until you master you dodges and memorize his patterns completely.
One of the first things that will probably happen is he will herd you into a wall (or glitch you into it). killing you outright because you cannot dodge away. Staying away from the walls during this battle is vital as his lumbering form can block your escape. Some of his three hit attacks are also quite dangerous (making you think they are only two hits and then adding a final attack). However, the biggest impact on the battle is when he drops past 80% and 60% health respectively. At 80% health, he will glow and the room will darken. During this time his flame will intensify and add a small AoE burn if the player gets too close to him. During the activation sequence of this, attacks do a third or quarter of the damage (arrows do nothing), so casters should make sure not to waste their powerful spells during this. At 60% the smelter demon will stop and plunge his sword into the flames of his body. This wreathes it in flames, making his attacks far more lethal and adding additional effects to them. Once again, during this damage is reduced significantly.
As to surviving this boss, increase your flame defense as much as possible. Even casters will be able to survive at least one hit with enough of it. Players may want to use the flame quartz ring +1 to reduce damage taken. You can summon Lucatiel as an NPC ally during this fight as well. Poison can be an effective tactic to use against him (dealing up to a sixth of his health per effect). Melee characters should max out their fire defense as much as possible and engage him directly. Ranged characters will need to learn his swing patterns and shoot after each attack to deal damage. It is a very difficult battle (unless you have max fire resist) and may require many attempts, so hang in there, He will eventually fall.
Wow, now that pain in the ass is out of the way we can move on. A set of stairs should be visible on the other side of the boss room. Climb up them and turn around at the top to find a chest with a Porcine Shield and a Flame Butterfly inside. Turn back around and head forwards to find the second bonfire of the area. For those that like an extra challenge, you can go back downstairs to the boss room and take on the pursuer (yes, even if you killed him before) once again. If you defeat him, he drops a few thousand souls and the Ring of Blades +1.
When you are ready to move on from the bonfire, open the nearby door. At the end of this walkway should be a captain to take care of and a door to your right that leads to a bridge with two turtle knights at the end (this is where we left off exploring before in our earlier item search). As you step onto the bridge, one of the turtle knights will move forward to engage you and the other may or may not begin slamming his weapon into the bridge. If he does this enough it will smash a hole in the bridge, but it is relatively easy to jump over.
Casters with the lightning spear miracle will be able to make short work of the turtle knights but baiting their slow attacks and using hit and run tactics will whittle them down quickly no matter what class you are. Jump over the gap (if the second turtle knight succeeded in breaking through the bridge) and stop in the doorway between rooms. The next room is full of platforms and quite a few enemies. A greatbow knight is on a raised platform slightly to the right when looking through the door. Cautious players should use ranged attacks to get rid of it before moving through the doorway. A lever near the door can be pulled to kill off two turtle knights on the walkway in front of you (only pull it once though or else you will cut off access to some nice items). Now the initial part of the room is clear, look to the left to see a door in the wall. Inside is a pharro's device that reveals a hidden door in the nearby wall. Attack the wall to access a ladder in the room beyond. At the top you will find a lower ledge with a bonfire on it. A nearby chest can be opened to retrieve a Thunder Quartz Ring +1. Drop down and light the bonfire.
The ladder next to it leads up to the Belfry Sol. You can skip to that section if you want to explore it (it is quite short and self-contained) before continuing deeper into the Iron Keep. If you do decide to investigate Belfry Sol, you will re-enter the Iron Keep on a ledge just above this bonfire. You can open a hidden door in the wall on this ledge to find two chests. The chests contain a Black Knight Greatsword, a Protective Chime and a Grand Spirit Tree Shield. Simply drop back down to the bonfire below or drop down to the path further down to resume progress in this area.
Make your way back to the walkway below (traveling from the bonfire just after the smelter demon) to continue onwards. If you have ranged attacks, you should be able to take out the two katana knights on the platforms as well as the archer on the small walkway to the left (melee characters will just have to deal with the archer first and then confront the knights on the platforms afterward). Move down to the walkway on the left (looking for pressure plates) and kill the crystal lizard in the way. The pressure plates here release a stream of lava onto the walkway and there are a few blocking your path to the end. At the end of this walkway is a corpse holding a Large Soul of a Proud Knight and a Radiant Life Gem. Further ahead is another magma path that has a Fire Seed and further along a Chaos Storm spell inside a chest. This is the longest and most dangerous path so only attempt it with over 1000 fire resistance.
Head back up to the platforms (with the flaming bull statues and head for the platform on the left first. Deal with the katana knight first (if you didn't earlier) and pick up the Large Soul of a Nameless Soldier off the body here. Time your run past the flaming bull statues and wait at the base of the ladder for a second. The platform leading to the other side will tip down if you walk on it. This leaves the narrow strip next to it as the safe walkway, so be careful when crossing to the far side. Ignore the ladder for now and walk across to the far side (staying off the platform to avoid lava pit death). Three small flaming bull statues will be straight ahead with another larger one to the right. Past the large statue is a turtle knight to defeat. Shoot through the flames or sprint past and engage him (you could also lure him back to the narrow platform path). Behind where he was standing is a body with a Large Soul of a Nameless Soldier and a Monastery Charm. Head back to the ladder we just ignored to move on (we will come back to the mist door from the other side, so for now head back to the ladder).
At the top of the ladder, there are water vases around the room as well as a Mimic chest that can be killed to obtain the Lightning Winged Spear and Dark Armor. Climb up the stairs next to it and follow the walkway to the far end for a chest containing Destructive Great Arrows. Ascend the ladder next to the chest to reach another small room with a pharro's device that generates water. The nearby stairs lead to a rooftop with three greatbow knights lying in wait. Pick them off from the stairwell with ranged attacks or rush them before they can swap to their swords if you are a melee class. The body on the left side of the are has a Simpleton's Spice, while the right side has a chest with a Black Knight Greataxe inside.
The path back down can be dangerous, so take your time and line up all the drops carefully to make sure you survive and get all the items in one trip. Drop down to the first bridge, then the next down and a third. On the third bridge is a body with a Cracked Red Eye Orb on it and a Torch. Drop down from here onto the next bridge and then drop down once more onto a long bridge that stretches the length of the room. From here, carefully drop onto the rim of the melting pot and grab the Covetous Gold Serpent Ring from the body inside. Walk off onto the lower walkway and engage the katana knight at the far end (avoid rolling at all costs). You should be able to drop off this lower bridge onto a set of stairs that has the mist door we passed up at the top. You can pass through it now if you like but it just leads back to the earlier room. To progress, head back to the stairs and enter the door at the bottom.
This narrow path has a turtle knight waiting as you round the first corner, so be ready to deal with him. Just behind where he was standing is a guillotine with a switch on the wall next to it. This acts like a gate that will drop down shortly after you raise it by pulling the switch. If you aren't careful with your timing this can be terminal. Pull the switch and run under it to engage another turtle knight around the next corner. The room behind where he was standing is full of flaming bull statues. They will flame every few seconds, leaving a short gap in timing for you to run past them. Ignore the corpse with the item on the ground for now as we will be returning here shortly after we turn off the statues. A ladder on the wall here leads up to a second ladder and at the top of that you will find the final bonfire of the area. Next to the bonfire is a set of metal stairs that leads up to a switch. This switch deactivates all the flaming bull statues in Iron Keep (making our lives a lot easier).
Return back down to the room below to retrieve the Lightning Short Bow +1 from the body safely. The nearby set of stairs leads down to another turtle knight. Past him is a large open area that is the setting for your final boss fight of the area. Head all the way down to the building below and travel through the mist door to take on the boss.
Boss: Old Iron King
Personal Death Count: 0
Claw Swipe: The old iron king will draw his open hand back to the side and then claw in an arc across the platform. Move backwards to avoid this simple attack. Long recovery time makes for a good attack opportunity.
Fire Stream: The old iron king will raise both fists in the air and then lean forward and release a stream of fire in a straight line, then will move his aim towards the player (moving the stream). He will not go right to the edge of the platform when moving (see the video for positioning) so ranged characters can take advantage of this. Move sideways away from the stream to keep safe.
Flame Smash: He will raise both fists (with flames coming out of them) overhead and then slam them down onto the platform towards the player, sending forwards a wave of flame. Very slow but damaging attack. He can also perform a roar at the end of the attack that knocks back players if they are too close. Has a long recovery time so roll to the side to avoid it and retaliate.
Melting Beam: The old iron king will pull his fist back and then jab it forwards, releasing a beam in a straight line from his hand. He will be unable to move after releasing the beam so this is the perfect opportunity to heal or continue attacking. Simply move or roll to the side to avoid this attack.
Punch: A quick downward punching attack towards the players position. Roll to the side to dodge this attack.
The second great soul battle commences. If you defeated the smelter demon in the earlier half of this area, this boss will seem like a joke. Casters can keep their distance quite easily and rain spells into him for quite high damage. Melee characters will be able to bait his slow recovery attacks and lay into him for massive damage. Casters will also want to take advantage of the binoculars and non lock on casting to get in several hits before he even reaches the platform at the beginning of the battle (archers will be able to fire with manual aim as well). His position on the battlefield can change as the battle goes on. This can allow you to use the buildings as cover (although his beam attack will ignore walls). Poison attacks also work quite well against this boss, taking down his health quite fast. In all honesty he shouldn't pose much of a threat after learning his attack patterns and should be pretty easy to take down.
After defeating the Old Iron King, travel around the walkway to pick up Sublime Bone Dust from the chest and light the primal bonfire down the stairs to return to Majula. Another great soul down people.