Lucifer Sage - their alias/nickname being "Lucius" - is involved with Ether Astrum's cult, but they might be a spy: Similar to Blair, it’s unclear just what their motivations are. Lucius is a very kind and empathetic doctor, somewhat nerdy. They are also a wizard. Their actual gender identity is unclear, but Lucius takes on the guise of a man when interacting with Ether Astrum's cult. They have a voice that would be very deep for a woman, yet very high for a man.I imagine their voice would sound like the YouTube animator/singer Puccagarukiss, especially during Hyde's bit of this cover of Confrontation. If you can't imitate Puccagarukiss, a slightly deeper version of Garnet from Steven Universe will suffice.

Lucius might have a British accent, but if you are not British, and can’t imitate a convincing British accent, that’s totally fine if you still manage to sound somewhat like this character.