With some time invested I’ve noticed resources starting to pile up that could be recycled, and as always, I’d like to suggest some potential uses for them.
Amber quickly stacks up once you get multipliers to your loot bonus. In traditional Feng Shui, amber is burned down to an oil for use during festivals and other occasions, and is thought to bring good luck and clear-mindedness. An Incense Burner NPC or utility could burn stacks of amber, maybe 10x or 20x at a time or a comparable amount, in order to produce a Fortune bonus. If you really wanted to be complex, you could offer different bonuses based on what the Amber type is, but that sounds needlessly complex to me.
Creatures tend to stack up in old dusty corners for me, because I didn’t have access to the traits I wanted immediately and needed to make half-assed teams. In older games you could breed them for Heredity or Gene Strength, which worked, but S:U doesn’t have a way to recycle creatures directly yet aside from fusing them again (and I don’t know what happens when you fuse a fusion, no). I’d suggest attaching an option to the Arena that lets you release the creature from your service to go fight in the Arena, and every time you participate in the Arena you get a small bonus to Glory based on how strong your creature was.
Curios, Slates, and Trick slot materials also stack up, if at a notably slower pace. I’d throw out a suggestion to find an Archeologist out wandering the Realms that agrees to head back to the Castle, and then you can donate sets of Trick slot materials to him, which he can study to find clues about the locations of Nether Stones out in the world. How this plays out, I don’t know, because it should not be easy to find Nether Stones - I don’t necessarily think just a bar that fills up to produce one Nether Stone is a good idea. Maybe donating to him increases the loot chance of finding a Nether Stone over time, until you get one, causing it to reset? Food for thought.