LIFE AFTER LEVEL 20
After reaching level 20, the focus of Destiny changes from a linear level progression (based on earned experience) to one that revolves around finding objects with the new "light" stat. This stat can be seen on gear alongside the usual intelligence, strength and discipline.
Items have various tiers of rarity (or strength depending on how you look at it) similar to most other MMOs. White (common) and green (uncommon) items are regular drops for players under level eighteen. Some blue (rare) items may be rewarded from strike participation or story rewards but will not drop from enemies until the player reaches level eighteen. After level eighteen, legendary (purple) items have a chance to drop from slain enemies. The final tier, yellow (exotic) is the rarest of rare with regards to drop rate but can be obtained via other methods.
Ways of obtaining legendary and exotic gear:
As these are the game changers of Destiny's after 20 levelling system, finding new high tier gear is what makes the difference in what you can accomplish and access. Below are some of the methods you can use to obtain these powerful items.
Gaining reputation with factions (see factions and currency section for details) and spending vanguard or crucible marks to buy legendary equipment.
Saving strange coins (obtained via daily events or decrypting engrams) and/ or motes of light to buy exotic equipment and engrams when the vendor appears in the tower (currently on weekends).
Drop rate is the same no matter what area, strike, mission you are playing in. Therefore killing a lot of weak, small enemies will give you much better rewards than a few tough and time consuming foes (see item farming section of the guide for details).
Completing raids or high level events (however these only become accessible after meeting the required level or gear cut offs).
Playing PvP (any mode) in the Crucible. The loot rewards in the Crucible are randomly selected, so you may get a legendary or exotic for barely paying attention. There is no difference in resulting rewards for playing better or worse. A person in last place may get a legendary shotgun while the person in first gets a rare set of gauntlets or pallete swap item.
Exotic bounties. These are rare and allow the player to go through several areas but will reward you with a guaranteed exotic weapon. Apparently, completing a lot of bounties will make these appear more often.