The Invasion began with the launch of patch 1.11. Outside each major city and at various high level zones in the game players could encounter floating undead constructs called Necropoleis or necropolises with at least four groups of undead creatures spread out in a diamond formation below. At each point lay a necrotic crystal guarded by legions of undead. Upon destroying these crystals players could render the accompanying necropolis inert for a time and score a “victory” against the Scourge.