covaithe
Explorer
I've put your tokens out without a great deal of thought; feel free to post initial positions with your initiative rolls; anywhere completely within 5 squares of the stairwells on your end of the arena.
Roll initiative separately for each group of identical monsters. No duplicates in this fight, so the each get their own roll.
The braziers in the corners of the arena are firmly bolted to the ground and can't be moved. Anyone starting their turn in one of those squares (presumably as a result of being forced there) takes 1d6 fire damage. Having one of the pillars in the middle between you and an enemy provides cover.