Seeker, Slayer, Survivor, the second DLC for Pillars of Eternity 2, will feature playable arenas tied to artefacts collected by the player. Once a player collects an artefact, they return to the arena, hand it in, and there will be between 1 to 3 fights which must be completed in sequence. Beat them all, and the player earns a bonus at the end.
Source: N4G PC Seeker, Slayer, Survivor DLC features arena battles and artefacts