So I've been thinking about how this can be done, and the new PVP mode (feast) gave me some ideas about how to make this game mode really cool, without spending a tonne of development time (looking at you LoV).
Basically it is a horde mode in a halitali-like arena for a party of 4, the enemies come in waves and become increasingly strong. The waves are split into blocks of 5, and at the end of every 5 waves you get a treasure coffer, which awards MGP and a status upon opening (mandatory opening to continue). The status's are random but are mostly bad and last either indefinately, or for the next 5 waves depending on balance. These and are designed to make later waves more difficulty and can be things like infirmary, bleed, and slow.
As you delve deeper, harder types of mobs could start appearing and even boss monsters (imagine fighting a cyclops and ultima at the same time).
I'd love to know what people think of this idea, especially what could make it more enjoyable
Edit: I wonder how much inspiration could be taken from the Olympus coliseum from Kingdom hearts
