what are fight clubs in PvP?

[modern sentinel]

It's pretty much a session where the host summons other players placing their red sign (some also allow invaders, but these do tend to try and ruin things)

In a fight club, you're not trying to kill the host, but you take turns to kill other summoned spirits in a 1v1 duel

Winner stays to fight the next until death

And that's the cycle until the host has enough and gets himself killed