From Lexicanum

Kyublai was a Great Khan of the White Scars Chapter in the 41st millennium.¹ He held this position for over a hundred years.²

During the centuary as Great Khan he commissioned the death of Daemon Prince Kernax Voldorius, a great enemy of the Chapter. The task was executed by Kor'sarro Khan. ²

In 943.M41 Kyublai disappeared fighting forces of the Dark Eldar. His successor Jubal Khan leads the Chapter to this day. ¹

Sources

• ¹:US WD256/UK WD257, Index Astartes I: The White Scars
• ²:Codex: Space Marines (5th Edition), p.42