[Cybsled]

At the end of the WC2 expansion, all the portals on Draenor have had the effect of destabilizing the planet. Ner'Zul was the one who did it if I remember correctly (who in time became the Lich King after the Burning Legion pwnt him...he took the wrong portal!). The Dark Portal on the Draenor side supposedly blew up (which ends up not being the case), thus they though the orc threat was gone forever save for the dudes that were still on Azeroth (which sets the theme for WC3).

Anyways, Draenor doesn't get totally destroyed. It basically just gets ripped apart, in some cases mutated by the energies, and ends up in the Twisting Nether as a bunch of floating islands and shit. Draenor is then known as The Outlands. The life in Outlands is a combo of stuff that lived on Draenor pre-sundering (usually mutated) and things that live in the Nether, such as various demons and what have you. I imagine you'll find lots of remnants from WC2 in the area of the portal, and indeed the WC2 alliance heroes are still alive. Most of these heroes are the guys on the bridge leading into Stormwind, one of which is Sylvannis' sister.