Stages are just for the show (for the comic to have some awesome scenes and situations), you will be dueling in classic mods so that all would be fair and square.
But, in some cases, depending on the arena you get, it might happen that rules to win change during a duel.
Like in the Core Vault arena, by random chance, in the middle of the duel, you might have to fight (both duelist) against some GM, and if you lose that one fight - YOU DIE!
>:}
But, don't be scared, chances for that are very small, also, death in ToriWorld is not the end. All souls of Toriworld dwellers are kept in their Core Crystals (that they wear around their necks), so after some period of time you reborn.
That's how I explain that ppl have different look (changing sets and head textures) but same name in Toribash (Toriworld).