Excess battlefield death causes unwanted demons to be ejected upward from Sheol and randomly possess weakened bodies.
The system announces that souls rain upward and Sheol is overflowing. Powers in hell fling unwanted minions into the living world, where they cling to recently fallen or weakened shells.
Large battles greatly increase the chance of mass possession. Cuba enters an active area-wide event because the seal-crab war, divine unrest, and ocean-spread zombies create both the death pressure and abundant hosts.
Mordecai says this normally begins near the end of the ninth floor and appears earlier on later floors as part of Ascendency setup. The current eighth-floor timing is dangerously premature.
Dark figures falling upward from a red underworld into corpses scattered across a battlefield.
Demon Eviction turns every fresh corpse and weak undead creature into a potential intelligent abductor.