Is it worth it? I've collected about 2 bones from each of the monsters I could find (Kirin, Drago, Big, Amon), except for Kirin which I completed. Kirin, even with the mute seed upgrade is only level 32. Now that I'm level 40ish with level 45ish monsters, Kirin is kind of worthless. Is there any reason to hold on to him and go and assemble the other monsters?
Also, is Tinygon worth keeping around? He's had good HP for a while, but he's starting to lose usefulnes as well. There are fewer monster slots in this game than in the first game, so it doesn't make a whole lot of sense to keep around special monsters if they're not going to be helpful.
I don't believe Kirin is used in any special fusions or anything, so you can probably get rid of any monsters that you're not using! The bone monsters are rather useful if you're rushing through the game, but if you get a high enough level, they become obsolete!
Drago revives to level 35; Amon to 40. Neither one of them becomes too much better. The demon you get from the big bones starts at 40 and jumps to 50 when you revive him with nearly 800 health. I haven't gotten to the end, but when I got him I was just before fighting the pirates, and the alternatives were around 35.
"Aku-Soku-Zan. To Destroy Evil Instantaniously. It is the rule we, the Shinsengumi will follow until we die." - Hajime Saitou