El Pazzo was a powerful member of Clan Mulielo . He's been officially declared dead, but rumors say he's still alive somewhere on Pazz'tar and disguised as an old man, who's usually seen eating arancini at night and disappears immediately after.
During the Che'kataar War, he used his face warping ability to work as a spy, giving a significant tactical advantage, over the years, to Clan Mulielo. His weakness was the lack of control of his eyes' color, which seemed to change unpredictably, potentially revealing his false identity. When put in danger, his subconscious mind was capable of triggering a Berserk status as a last resort, often giving him the edge in battle for a short period of time, in order to escape and get back to the headquarter.
The circumstances in which he died still remain a mistery, as his body was never found and the Clan declared his official death, based solely on his long and unexpected disappearance. Some speculate other members of the Clan itself might've killed him, but there's other rumors contraddicting this theory.