Undead Citadel achievements

Finish level "The wall" (4)

Finish level "Entrance" (1)

Finish level "The Maze" (8)

Survive for more than 10 waves in the Horde mode

Finish level "Tower" (10)

Finish level "Bridge" (3)

Kill an enemy at 30m

Finish level "Inner walls" (9)

Kill 500 undead enemies

Get an archer to kill another enemy

Finish level "Runway" (5)

Finish level "Gates" (2)