According to Monroe, only an immortal can get rid of Loki completely, so it can be assumed that the trolls might be immortal.
At the end of the same episode, Thor summons a few new ones to banish Loki again.
When we see them in the episode, they have blue skin, wear green tunics and have red hair.
As cited by Jasmine, the Trelleckians are one in just a handful of blue trolls and that there haven't been any blue troll sightings in a long time. They have pointy ears and misplaced or missing teeth. They carry hammers and are dressed similar to depictions of Scandinavian mythology.
- Ah-mah says that there haven't been any blue troll sightings in a long time but later in a season 2 episode "Dog Show Afternoon", June herself hires a few Securitos trolls, who happen to be blue.