We started virology today and I had an idea for a troll who was infected with a particularly virulent virus. The virus multiplies rapidly and in any other creature would kill its host in hours due to the massive tissue destruction and hemorrhage. However, the troll's natural regeneration allows it to maintain homeostasis even while it sloughs off pounds of flesh as new virus.
This is gross on two levels. One, the thought of an actual, macroscopic lump of viral material and two, the thought of a troll who is constantly dripping with this macroscopic material and wants to kill and eat you. A particularly smart troll might try to evenly distribute the virus across its arms or body; otherwise, a large viral abscess could serve as a built-in "pot of poison" that it could dip its hands in before attacking.