Names for book characters?

Heyyyy!

I want to write a book about two siblings, a 20-year-old and a 21-year-old. I've already planned quite a lot, but not everything yet. For example, I don't know who the villain is (I know that's not very clever) or what the names of some of the supporting characters will be. It takes place in a fantasy world, so it doesn't really matter where the names come from. The siblings are called Iska and Talvie, and Iska's initial enemy is called Serafina, but I'm not entirely sure about that yet. However, it would fit because she has the element of fire. (Iska and Talvie are both water). It will mainly be about the three of them. They're all in a desert robber gang that raids villages and towns. Serafina is always in a clique, with other fire girls and boys. The names should be unusual and ideally have a relevant meaning, but that's not necessary. If you know any good names, I'd be grateful!

I need names for the following people:

the boss of the robbers (royal and powerful)

The people from Serafina's clique (fire)

a hostage taken by the robbers (no matter whether male or female)

possibly also alternatives to serafina (fire)

Thanks in advance!

gggglg