There's a unique charm to the player-ran fight clubs in previous From Software games, but joining those means signing up for waiting and faff. The three PvP colosseums that opened up in Elden Ring today let you jump straight into wailing on folks, each offering different rulesets, from 6-player deathmatches with endless respawns to more gentlemanly 1v1 duels.
Chumps who want to fight alongside their summonable Spirit Ashes have to go to their own special colosseum, for nerds.
If you're after big battles, Limgrave is the place to go. The colosseum there features two modes, "United Combat and Combat Ordeal". United Combat is where "two teams fight in timed battles with the ability to respawn", with victory going to whichever team did the most murders. Combat Ordeal is a free-for-all, also with respawns, where points are clocked up for killing and lost for dying. Whoever has the most when the timer hits zero wins.
The Royal Colosseum in Leyndeel, meanwhile, is all about duels. No respawns, just a good ol' 1v1 showdown.
The Caelid Colosseum includes all the modes above, but lets you summon Spirit Ashes. So I suppose if you want really big battles, head over there and try to keep your head above water while five other players and their summons all come for your head.
You can hop into the colloseums on your own, or use group passwords to match with friends.
I'm curious to see whether players try to bring their own rules to these, like forbidding healing flasks. That's how the Dark Souls 3 fight club that Brendy (RPS in peace) rode along with did things, communicating the ban by having their umpire jump down and wave their torch in offending players faces. I wonder if the more rigid, official setting might lead players defaulting to the assumption that anything enabled goes, which would be a shame. Convenience is swell but player-enforced customs are special.
The Colosseum update also added some new hairstyles, along with various balance adjustments. Patch notes are here.