Here is the full list of all 13 NECROPOLIS achievements worth 1,000 gamerscore.
Recovered your first Codex.
Has slain an enemy using a power attack.
Has consumed something without even knowing what it is.
Has been slain in the Necropolis.
Has crafted something (mostly) useful.
Traverse down a Level without using an elevator.
Recover all Codexes.
Die to a trap.
Escape the Necropolis.
Obtain fifteen thousand gems.
Learn to craft everything.
Survive longer than your average dungeon delver.
Find and equip a new suit of armor.