Conquest of the Horde

I'm looking to learn something on Fel Energy, how its used, why someone would use it o.o aside from summoning demons, and its consequences. I know its evil and dark and the like.

1) It's more of a teaching thing, I guess. The Orcs learned from Demons, Humans/Gnomes from Orcs, Blood Elves from probably Illidari.
2) It's corrupted Arcane. Very powerful, but horrible for the body.
3) You become a Felsworn. Lawful Evil, wings, unattractive, etc.

These two guides in the articles and guides forum might help!
viewtopic.php?f=48&t=9155
viewtopic.php?f=48&t=5370

And this guide to warlocks on WoW Insider is pretty nice too!
http://wow.joystiq.com/2008/11/30/all-t ... a-warlock/

wowwiki is your friend.

http://www.wowpedia.org/Fel

thank you everyone! this has been very helpful