Surnames for my characters?

I need help with surnames!

I’m writing a story that takes place in an old, medieval style kingdom. Basically, it’s about an assassin named Elaray (often called Ray) who is on a mission to free her best friend (named Ilyona) from execution because Ilyona (also assassin) was caught during a mission. Ilyona is held in the dungeons under the castle until her execution and the only way in is through the castle, so Elaray has to pretend to be a court lady and seduce the crown prince (named Ezric) to get in to the castle and the dungeons. But during all this, she falls for the second born prince (named Cazriel) which messes up her whole plan.

Now, I need surnames for these people:

  • Elaray (she originally comes from a poor family in a small village. I’d like something with like three or four syllables and maybe for it to start with G or S? And maybe for it to sound a little intimidating, since she’s a notorious assassin)

  • Ilyona (comes from a middle class family)

  • the royal family: King Kedron, Queen Morbella, Crown Prince Ezric, Second born Prince Cazriel and Princess Nephelia (something powerful with many syllables. I especially want the king’s name to sound intimidating, so something that fits with Kedron and makes it sound intimidating and powerful)

  • Gavinus (the man who trained Elaray and Ilyona into assassins. Preferably four syllables and something ending with -er

Elaray [name_m]Gulliver[/name_m]
Elaray Savage
Elaray Guillebeaux
Elaray Grigoras
Elaray Skalbeck
Elaray Spedoske

[name_f]Ilyona[/name_f] Alexeyev
[name_f]Ilyona[/name_f] Massoumbert
[name_f]Ilyona[/name_f] Montarac

[name_u]Royal[/name_u] family: Laurier, Villarreal, Vandenberg, LeCoultre, Merovingian

Gavinus Oppenheimer
Gavinus Mirthcleaver