The third and final part of the Heaven Sent operation. The toughest mission in the game so far, so bring your toughest fighters- including at least one shield breaker and one armor breaker specialist.
Note also that this marks a point of not return for the early part of the game. While you will get access to more agents and missions afterward, the city itself will become more hostile, and every time you take out a major enemy objective, some of the areas you've captured will be lost.
Tag the marker outside the burning temple to begin.
The first part of the mission is to drive through three markers while Hammersmith takes shots at you with his space laser.
You have to hit the markers in order- just follow your objective. No need to drive recklessly- you're not under a time limit, and the laser is fairly easy to dodge, so long as you don't put yourself into a wall. The laser doesn't do as much damage as you'd expect either, so just drive safe and hit all three gates.
Hitting the third will lead you to the lair entrance, but there are still several consoles to hack before you can enter (three, in fact. Always in threes). The first is under the same bridge where Braddock gets ambushed when chasing Hauser. True to form, you'll be ambushed here as well. Clear out the swarm and helltroopers, then hack the console behind the crystal.
Go back topside to be hit by swarmtroopers on the ground and helltroopers on a rooftop. The close spaces of the rooftops make them ideal for area attacks.
Clear the rooftops and hack the second console, then follow your marker to console three, a recalcitrant cow.
Interacting with it summons a hellfire turret. The description says to keep moving or die, but you're usually better off firing from cover.
It's got a layer of armor, but if you're quick on the draw with an armorbreaker, you can half kill the thing before it even starts firing.
Kill it all the way to reveal lair access via a hackable barrel, then drop on in. The first challenge room has a few enemies and some more turrets, both hellfire and plasma. The plasma turrets don't activate right away, but when they do they fire slow-moving energy globes. You can shoot these globes to destroy them prematurely, even inflicting damage on the cannon if you shoot them close enough.
The best strategy here is to kill the guards from cover, then advance on and destroy the turrets as they appear. The overall goal is to destroy the marked power conduits- most are in the main chamber, but one is in a high room that you have to access via the stairs. Note the health dispenser to the right of the stairs, if you've gotten hit.
Advance to the next room, with the refreshingly simple goal of Kill All Enemies. Do so.
The initial swarmtroopers are easily dispatched, but the final shocktrooper can be a bit of a pain. If he's closing too quickly for you to finish him off, take to the upper levels where you've got a better line of sight, and he's less mobile.
Killing him summons another wave of swarmtroopers, capped off by a shocktrooper commander. As before, the upper levels will give you a tactical advantage against his quick charges and even quicker shield regen.
There's a health dispenser built into the electro-beam wall here if you need it, otherwise proceed to the next room, where you will be hit with toxic gas.
When scanning, keep careful note of the final indicator tab- it'll flip up or down slightly to indicate if your objective is on another level. In this case, the console you need may be directly above the one you just hacked, which can be confusing if you're not looking for the signs. Remember also that the destination console will have the interact icon hovering nearby.
Hit all three terminals, then exit the room from the top level. You may want to linger a bit in the antechamber to recoup lost health- the next chamber is the Big Fight.
The first objective is to destroy the three turrets. You can easily slag the center one from your perch, but you'll probably want to jump down to ground level for the other two, where you can more easily find cover from Hammersmith.
Take out the arc turret to the right first, ideally from the right-hand side, to avoid getting smacking in the back by a plasma ball, then head back left to destroy the plasma turret.
This triggers the next phase. Hammersmith has two main attacks here- a barrage of quick, tiny dark matter balls you need to avoid, and giant charged-up balls you need to shoot. Once you destroy the latter, Hammersmith himself is briefly vulnerable and can be fired on normally- preferably by an armor piercer.
Taking out his armor triggers the next phase. Markers indicate shield generators that need to be destroyed, but your weapons can't scratch them. Instead, hide behind them and let Hammersmith's electrobeams do the work.
Every time a generator goes down, attack the central Beam Generator. For some reason it's almost impossible to damage at an angle- you have to fire right into it.
You'll need to do this for each of the generators. Hammersmith will unleash a wave of troopers, then more of the small dark-matter balls, and eventually electro missiles to stop you, but you can almost completely ignore them as you bound from shield generator to shield generator. Put the final bullet into the beam generator to overload the system, end the fight, and complete the mission.
You'll walk away with the usual XP, cash, and gadgets, plus an upgrade core and access to new agents. Note that the core gameplay will change as well. The city is now wracked by more LEGION activity, including doomsday devices. LEGION will also slowly recapture assets you've claimed, and taking back them becomes harder.