Really useful DLC that makes capturing monsters you already had much easier. I do feel like this could've been in base game though, possibly as a late game unlockable dungeon. I'm not too upset by this being locked behind an additional paywall but that does make my score of it go down slightly.

Edit after beating the game's main storyline:
Okay this is actually way more useful in late and post game when you have multiple monsters that are only obtainable through synthesis only leading to more monsters that are synthesis only via the other synthesis only monsters. Almost feels like this mode is the only thing keeping me sane trying to get every monster. My rating isn't changing though since it still kinda sucks it's behind a pay well but def better this exists at all than if it didn't. Def the most worthwhile of the day one paid DLC.