What, threads for general Arena admin stuff?

Depending on how Mahz does it, I guess one thread for the leaderboards.

One where members can sign up for Arena, with an easy to access list of combatants. This would also be a good place to put the 'ruleset' for Arena, for people who aren't interested in creating their own individual rules. Considering most tournaments tend to run in T1 Eden, that would probably be the one.

Maybe another separate one for 'certified' judges, so they can be contacted when they're required.

Arena Battleground thread, possibly.

And finally, maybe a general arena chat thread, like this one.

That's all I can think of, provided this is what you meant.