This would reverse the recipes of a standard Mana Pool, sucking the Mana out of Mana Steel/Pearl/Diamonds, removing the Mana from Petals, and so on - not necessarily returning all or even most of the Mana. Due to the one-per-pool nature of Catalysts, it can't reverse the recipes of the Alchemy Catalyst or (this wouldn't even make sense) the Conjuration Catalyst.