Settlement scavengers, shipboard pests, and plague-adjacent warning signs in granaries, docks, and ruins.
Rats belong wherever people store grain, sail ships, or leave refuse. In Viking-inspired play they are especially useful around docks, winter stores, and abandoned halls.
Rats are not central to Norse myth, but they make strong practical horror. A rat swarm in a longhouse says something has gone wrong with food, sanitation, or the dead.
Use rats as infestation, famine pressure, disease sign, or the first visible clue of necromancy below a settlement.
DM-only encounter details, stat blocks, and running notes are kept at Rats (DM).