I’m about 20 hours into it so far, and just started doing some amalgamations to change some of my Jewel Monsters into bigger, badder, different versions.
This is really where the game shines, and differentiates itself from Pokemon games. Once you get access to the Jewel Meisters, you can fuse different crystals into your existing Jewel Monsters to add abilities, or affect their stats, or transform them into different evolutions.
For example, say you capture a Baby Wyvern with a Wind Crystal. Now, you can summon and fight and level up this creature, and it will learn some new abilities as it progresses. But, to get the most effectiveness out of it, you can fuse enough Wind shards into it to evolve it into a standard Wyvern (Wind Element), with better stats and new abilities. Alternately, you can fuse Fire shards into it to evolve it into a Fire Wyvern, and change it’s element type to Fire; it still retains its previous Wind-element abilities, but now it adds and learns Fire element skills to supplement or replace these. Or, you can fuse Dark shards into it to evolve it into a Dark Wyvern. These secondary forms can evolve into further forms, depending on what you fuse into them.
Even without evolving the monsters, fusing different elements into them offers abilities outside their norm, and also affects the elemental strengths and weaknesses of the creature. For example, a Fire element creature is strong against Ice, but weak against Water. Furthermore, since Fire is affiliated with the Light element, it is both a stronger attacker and weaker defender against Dark affiliated elements. BUT, if you fuse some Thunder shards into this Fire creature, it will gain some abilities and traits of that element; since Thunder is strong against Water, this will help shore up this creature’s weakness against Water, but also convey more weakness against Earth (Thunder is weak to Earth).
One thing about this system is that the Jewel Fusions are on timers that take place in real-time, so that sometimes you’ll have a Fusion set up, but won’t be able to use the completed creature until several hours have passed in real life. I suppose it forces you to keep a diverse stable of Monsters, but some people might not like that aspect of the game.
Anyway, I’m still having a blast with it. I’ll see how it holds up once I get closer to the endgame.