Universal Cards can be used to:
1) Evolve a card, increasing its level cap from 10 to 15, replacing the requirement of a second copy of that card;
2) randomly shuffle a card's level 15 skill for a new one.
Each Universal Card has a star level (which must exactly match the other card it is being applied to) and a level. Level 10 Universal cards are acquired from assembling universal Scraps, while level 0 cards are acquired from other means (Events or Map rewards). Level 10 cards can be used for either purpose while level 0 cards can only be used to shuffle.