Making for a fun and original opponent for your superheroes, Lord Foulwind is a troll trapped here after finding a means to open a portal from, well, whatever fantasy world he came from. Capable of magic use as well as having normal troll capabilities like regeneration, he's smart enough to make a formidable foe.
There's plenty of background to help you bring him to (smelly) life, as well as several plot hooks to bring him into the action; and of course a full stat block to take care of the mechanics.
Lots of little touches make Lord Foulwind a bit more than just a classic fantasy monster dumped into a superpowered world, he has his place and his plans... and it's up to your party to deal with him before he makes even more of a problem of himself than he has already! A nice interpretation.