Kas the Betrayer
Kas the Betrayer (Or simply Kas as he was known upon birth) was a human that was mostly present in
15 B.B. He was a General to Vecna during the "Battle of a Thousand Eyes" before betraying him. Kas the Betrayer was also present in 350 A.B, as the leader of a demonic invasion upon Elion.
Kas is also known as The First Vampire, Kas The Bloody-Handed and simply The Betrayer.
15 B.B and Vecna's Army
Kas was once a valiant knight, highly skilled in martial combat. It was a common legend that Kas could enter a battle-field and leave victorious without a scratch upon his armour. It was his skill that drew Vecna's attention to him as a General for Vecna's army. Thirsty for battle, Kas agreed, on the condition that Vecna point him to the battle and issue no further orders until the battle was won. For his loyalty, Vecna bestowed Kas with a magical sword, "The Sword of Kas".
It was during the Battle of a Thousand Eyes that Kas was propositioned by Nerull to slay his master and halt the magical genocide with the reward being a godly Boon. Kas, hungry for power, obeyed Nerull and used the blade gifted to him by Vecna to make an attempt on his life.
Kas was able to remove Vecna's right eye and left hand before being struck down by Vecna.
Nerull, pitying Kas, bestowed him with a lesser Boon as a reward for at least weakening Vecna. Kas' soul was endowed with increased strength and speed at the cost of a insatiable (and literal) thirst for blood. This is now known as the Vampiric Curse. Kas would use this Boon in the Spirit Realm of Nerull's until his eventual escape.
350 A.B and the Demonic Invasion
In 350 A.B, Kas grew tired of eternal hunting in Nerull's domain and forged an alliance with the demons present there. Kas used his Boon to send visions to the vampires present in Elion to begin using blood rituals to pull his demons to the Material Plane, all the while using his own power to forge a large Demonic Flesh Gollum. When the moment was right, Kas fused himself to the Gollum and had his vampires pull the monstrosity into the Material Plane.
Kas destroyed much of Tacot and slowly made his way to The Shrine of Shattered Souls to destroy the remaining pieces of Pandora's soul as a final defiance of his once-leader. Kas and his Gollum were destroyed by The Furious Five in what is now known as The Battle of the Flesh Citadel.
The Gollum was destroyed by Morgan Ironfist after he nearly sacrificed himself by setting himself ablaze and hurling himself into an opening in the back of the monster's skull, destroying the "brain" (Kas' essence).
The site in which Kas was destroyed was made as a memorial to those lost during the invasion known as The Citadel of Kas the Betrayer.