ok, the reason you have double personas is because WoW has to accomadate for all of the different level of players. In the game, there are two Kael'Thas in order to accomadate the different players at the time. In lore, kael'thas is no longer a blood elf but is a felbood elf, servant to Kil'Jaedon. And the arthas persona thing, those are just ghosts or visions of the past. There is only one Arthas, the Lich King, and technically there is no Arthas, it is the Lich King, nothing more, nothing less. And also, warcraft 3 lore based on the games isnt very accurate, you actually have to look at the warcraft 3 lore based on the storyline, not the gaming experience. You never kill magtheridon in the game, it switches to a cinematic and he 'falls over', but they had to use a death/decay animation in order to accomadate for the game. So yea, there goes my explanations =P