As was announced a few days ago there will be a new, one day only collab dungeon for Ragnarok Odyssey Ace (PS Vita game) coming on 8/29. This will be a ‘rarity’ restricted dungeon in that every monster in your party and your friend leader must have a rarity of 4 stars of less. There will be a boss drop supposedly of this monster in the picture, although it is rumored some other ragnarok monsters may make an appearance. As you can see from the image it will have two difficulties and 5 battles.
See the full details here.