I like
Vespasian! It's wonderful in a "glamorous fictional villain who lives in a volcano" kind of way.
Semele is slimy and sounds like Semolina. I'd go with simple middle names -
Vespasian Leo and
Semele Maud.
masculine list:
https://www.behindthename.com/pnl/191050/124079feminine list:
https://www.behindthename.com/pnl/191050/124080