Kael is a pretty kind character in the Frozen Throne. He helped the nightelves after Tyrande helped him. He served Illidan because he had no choice after escape, and for his people. Unlike Arthas, Kael did not commit some terrible crime in the Frozen Throne. But in BC, he became the worst villian, a loyal servant of the Burning Legion, even turned aganist his people, used the Sunwell to summon Kil'jaeden. Kael finally died as a really ugly, evil monster. I feel like Blizzard wanted to totally destroy this character. The whole BC lore was pretty terrible.