actually u never see Illidan killin Magtheridon, he walks up to him in the cinematic and says his reign is over, shortly after tht Kil'Jaeden shows up, but i agree Illidan DID get cut by Frostmourne, but then again he is half demon and fairly powerful, personaly i think Blizzard made a HUGE mistake when they made key characthers killable in WoW, i mean....are we ever gonna see a new strategy game? and if it DOES show up, wht is it gonna be about? by tht time u prolly made it to Northrend and killed Arthas....which would suck big time if u ask me