Composite Ooze-Kin (5e Feat)
From D&D Wiki
Prerequisites: You must be an ooze-kin
You were made from several types of oozes, but only expressed traits from one type until now. Your dormant attributes now become active, making you part of an additional subrace of ooze-kin. Choose one ooze-kin subrace you aren't part of. You gain all of the racial traits of that subrace.