Abasdarhon's Castle

Does it make sense to take Clear Mind if there's a Lily bonus, or if they are the same?

It doesn't make sense. The Lily bonus is better; it works even outside of battle. Mental's companions won't be corrupted.

Added 1 minute ago

So, the main difference is that instead of choosing from a list, I have a custom one, right?

Correct.

What about the availability of unique skills?

In what sense, how many points will they cost?

Added 1 minute ago
Have you already agreed with whom you'll be playing as a Demon?