There are stories of a Poro that appeared to help Avarosa when her village was overhwelmed by raiders. When they first appeared, Avarosa had no idea what they were capable of. Gradually, Poros appeared, one by one, until the hall was full of them. Interestingly, them and their followers are some of the only poros seen using tools.
Together, these poros combine to make the most heartwarming sweatshirt this side of the Freljord.