By Compilation by Roncli.
Roots contains the following 14 levels as an arena:

Ancient of Days - Skyrat
Animosity - Sparhawk
Burning Indika 3 - Vander
Duality - Vertigo
Hardcore - Outrage/Rican
Inferno - Dr. Payne
Kataclysmica - Kruel
Keg Party - Duperman
Manga Gallery - KillsU2
Nocturnal - Nirvana
Pit of Despair - Fezzik
Skybox - Skyrat
Vamped - Nirvana/Horizon
Wildcard Castle - Skyrat/Zonerie

All levels used with written permission