Personally I think an illusionist should be about, you know, actually using illusions. If you're not messing with the oppponents mind it's not an illusionist.
An illusion can't actually harm you because it's not really there. It's purpose is to fool you, make you think there's something there that isnt, or to hide an object's or their own true form.
With that in mind, an illusionist should be able to cast any spell in their deck as an "illusion", but as soon as it interacts with anything that isn't an illusion in any way, it disappears and they regain most of the mana they spent on it. So you could have an illusion hand of bim heal an illusion ehren and then when they attack ehren ehren disappears so they know he was an illusion, and then they also know that hand of bim was an illusion too.
And every time the illusionist casts a spell, they would put a token on it, with one side saying either "real" or "illusion" and the other side blank. Whenever one of their spells interacts with a non illusion spell or object, they must flip the token to the non-blank side.
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