Here is the full list of all 13 NECROPOLIS achievements worth 1,000 gamerscore.
Has slain an enemy using a power attack.
Has survived longer than your average dungeon delver.
Recovered your first Codex.
Has consumed something without even knowing what it is.
Has found some fancy new duds.
Has crafted something (mostly) useful.
Has been slain in the Necropolis.
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.