I've only come back in the last few weeks, and still getting my head around the various update to the game, including Assist links. I've noticed different cards give different values, but oddly, not all characters have cards to them. I thought little about this until just recently when I was skimming through the available cards for enhancements and discovered a whole mass of cards that are grayed out. Most of them, I obviously do not have, and some stated they weren't available. However, there are some character that I have obtained, but their cards are still grayed out. Initially, I assumed it was because the higher sets are still locked somehow, but cards for characters like Enma and Shizune are grayed out but marked [Enhancement]. I'm curious as to know what is the deal with these cards.

EDIT: I have no idea why the title keeps putting an X in it. Not my doing.