(Possible dual role or tell me your preferred part)

Mina and Maive are two of Abysno's Generals, twin sisters transformed into maidens made of glass to serve his bidding. Mina is the more level-headed of the pair while Maive is more vain and rash than her sister; their targets for black diamonds often include people of wealth, stature and beauty. Both feel that there are none with greater beauty than themselves, and they are very dangerous fighters themselves, often using their combined powers in combat to commit a formidable force.

Voicewise, they can be identical twins (for a dual role) or if they are separate I could see Mina's voice being a bit deeper, while Maive is a bit higher pitched maybe a touch flighty