For Endgame content, there is a requirement to fight two monsters: Chimera and Hydra. This is necessary to obtain your Relic weapon. Unfortunately, it's extremely difficult to find a party for this, as there is no Duty Finder option for it.

In the future, will you add the Chimera and Hydra battles to the Duty Finder so it's easier to find parties for these runs? You could include them under "Trials" and it would fit the purpose just fine.