Currently there are only two sources for Catalysts: the relic store and the cabinet. Given the scarcity of sources for Catalysts, it’s fair to say obtaining them is not that easy. And aside from upgrading and using Catalysts, the only other thing you can do with them is sell them, which is kind of limiting and lame. Therefore, I think it would be fair to make Catalysts evolvable, just like fighters are. A similar premise as evolving fighters could be used for Catalysts, expect that to evolve a catalyst you need multiple copies of that exact same catalyst. Example: To evolve a bronze [Big Band Defenders] Armor Rating, you would need to sacrifice 3x bronze [Big Band Defenders] Armor Ratings. No other catalyst type will work, and it must be the same sub-type (i.e. character-specific, element-specific, or general). Evolving silver to gold would require 4 silvers of the same catalyst. These numbers could be tweaked for balancing purposes if they seem too low. The unique gold catalysts would be exempt from this system as they are unique, so no one could evolve their way to them. But this would make it a little easier to build a nice catalyst collection and also not make getting repeat Catalysts too wasteful. And given the number of variants for a single catalyst type, I think adding this system would not break the balance. P.S. - keys should also be evolvable.