Who is Vexen in Kingdom Hearts?

Answer 1

Vexen (No.IV) ("Chilly Academic") first appears in Chain of Memories, a Kingdom Hearts game for Gameboy Advance using cards as a means of battle. He controls Ice as a "scientist" among the Organization. As one of the first six, he originally served Master Ansem of Radiant Gardens, studying Heartless and hearts. Even, his original name, revealed in Birth By Sleep(PSP game), is mentioned in the Secret Ansem Reports in KH2, too. He conducted the Replica Project, which created Xion and Replica Riku.

Vexen thought that he'd garner respect rather than do missions, since he's one of the first six and eldest. He has the least completed missions in Where Nothing Gathers, a round, white room with very tall white chairs.

In Chain of Memories, he went to Castle Oblivion to help Marluxia continue the Replica Program. He was assigned to the Basement group, where all the Organization's brains (and possible traitors) were sent to work. However, Marluxia, Larxene, and Axel tried to overthrow the Organization. Marluxia tried to trick Vexen into fighting Sora, so Vexen tried to warn and save Sora, but Marluxia ordered Axel to kill Vexen.

Other appearances: Kingdom Hearts: Chain of Memories(GBA); Kingdom Hearts 2: Final Mix +(PS2, as a data/shadow fight); Kingdom Hearts RE: Chain of Memories (PS2); Kingdom Hearts 358/2 Days(DS); Kingdom Hearts: Birth By Sleep(PSP)(as Even).