A giant rat is a rat much larger than an ordinary one.1 Four attacked the party in the sewers beneath Argentum on 25 Coldrise, 1714 PSF, alongside four swarms of rats.2
History
Session 3
Temerity fought the rats in a rage and kept little memory of it. Afterwards she remembered running to stop two larger rats from reaching the others.2
Session 13
Near the Fardrimm Gate, miles beneath Argentum, the party found the tail and back left leg of a giant rat, and then the webs of the phase spiders.3