Primarily used pre-existing assets and collaged them together with some basic compositing and paint over the top to unify the lighting and rendering styles. Painted the Archon character from scratch (couldn't find an existing asset that worked for the space) and the background.
Original Arbiter Illustration by Peter Mohrbacher
https://www.artstation.com/bugmeyer
Jailer 3D character by Matt Mckeown
https://www.artstation.com/matthewmckeown
Denathrius 3D character by Jon McConnell
https://www.artstation.com/wabisabibobby
Winter Queen & Margrave by Blizzard Cinematics.