Location
The Doll's Training Arena
An arena in the sky, reached through the Cursed Doll, where a region's enemies can be fought again.
Ask the Cursed Doll and she will take you somewhere no road goes: an arena hung in the sky, with a waypoint of its own beneath it.
There she sets you against the real enemies of a region, one at a time, as many times as you like. In co-op the arena is shared, and when you leave, each of you returns to where you set out from. It is practice and nothing more. You earn half the usual experience, find no loot, and nothing that happens there has lasting consequences. Fall, and you are back on your feet beside her a few seconds later.
For the PvP duels and team battles of the arena hub, see The Arena.