Undying demon-headed rats Allister watched swarm a crawler's barge and refuse to stop attacking.
Crawler Allister recorded in the Dungeon Anarchist's Cookbook that he watched a group of Immortal Rats swarm another crawler's barge. Because they could not be killed, the defenders had to crush them with hammers and keep them at bay by force; their little demon heads were pulped and they still struggled to attack. Allister writes that their pained squeals still haunt him, and cites them as the reason the Immortality condition scares him.
Carl recalls the note directly when he sees Khepri's Immortal Bugs burning and screaming in the walls of the temple, unable to die.
Rats with small demonic heads, still moving and attacking after being crushed flat by hammers.
Allister's cautionary example of immortality as a curse rather than a gift.