Is there a planar colosseum type place?

[Yqatuba]

I could see Gorum being in charge of one, where creatures from all over the planes would come to fight (it would resurrect you the next day if you died, like with Ysgard in DND.)

[keftiu]

Ruby Phoenix volume 3 should detail some.

[Kasoh]

Alushinyrra in the Midnight Isles of the Abyss has Battlebliss, but that caters more to demons specifically, but it could have a variety of gladiators in it.

[Gamerskum]

Arent the midnight isles in Elysium now?

[CorvusMask]

Fist of the Ruby Phoenix volume 3 does indeed have four extraplanar tournaments, and two of them are very colosseum like :'D Like there is one tournament where infernal dukes sponsor mortals who want to save someone's unjustly captured soul from hell. Mortal has to sign up soul of three other relatives to take part in it and winning team's infernal duke gets to be one to make new edict.

The other one is velstrac one where velstracs capture people and make them fight each other.

(Also Midnight Isles are still in Abyss, Nocticula created new realm in Elysium)