Possible Clues:

• Adam and Eve's first
• Grendel's ancestor
• One imprisoned as a murderer
• Sounds as if one might stick the sound of what came from 1 across
• He killed 25 percent of the world's people
• Biblical sibling
• With a sound stick, able to have a brother, by the sound of it
• Abel's undoing
• Chastisement, say, for fratricide
• Guy raised by angry people?