Raziel finds clues about some weird creatures that look like him but seem to be long extinct as almost nothing is left by them. So he finds Janos Audron, a vampire that had an offhand mention as a very old inhuman monster. Only
it turns out he is one of the Ancients. Also not really a monster. However, Sarafan vampire hunters followed Raziel and managed to capture and kill Janos in front of Raz's eyes. Also,
it was the human Raziel who did it. This leads to Raziel (the playable one) to infiltrate the Sarafan stronghold for revenge.
Also, the death of Janos, made Vorador massacre six of the circle of nine.
The very beginning of Blood Omen. It wasn't just a random act of cruelty on the vampire's part as we were led to believe - it was just pure revenge.
Oh, and in the mean time, Moebius, along with Malek held Raziel away from this.
Moebius prevented Malek - the guardian of the circle, to actually guard them, that's why in the beginning of BO, Malek was late. And for this, he was punished some time later - his spirit bound to his armour and his body left to die. Rather cruel punishment. No wonder he turned butter and hateful.
And here comes the ironic turn of events. Raziel, Dumah, Rahab, Melchiah, Turel, Zephon - the true extend of Kain's joke is not only that he raised some of his greatest enemies as his greatest allies and comrades. It was also one of their own that made them die in the first place -
Raziel, former vampire hunter, former vampire, was the instrument of their destruction.
And when all is said and done, the best plot twists comes (at least for me): the Reaver blade, which Raziel used to slay his twice former brethren, turned to consume him. And then the realization hits him:
Raziel said:
...the ravenous, soul-devouring entity trapped in the blade was - and always had been - me.
This is why the blade was destroyed when Kain tried to strike me down - the Reaver could not devour its own soul. The paradox shattered the blade.
So - this was my terrible destiny - to play out this purgatorial cycle for all eternity...
I could not bear it - despair overwhelmed me.
And after the plot twist - surprise: Kain prevents Raziel's fate...only to turn things around once more as the history readjusts itself to this turn of events...