I like this, it's balanced and it works with Schrodinger's Cat, etc.
In the notes: I think immaterial is an effect, not a passive (look at a graboid for example).
Also, the card text makes it seem like the creature itself gains the HP, which I guess could make sense, except that it's immaterial. It probably means to give up to 5 (9) HP to the owner, right? It needs some rewording, I guess.
Hm..i'm not sure it works with kitty; After all, kitty only has 1 or 3 health, and dead/alive is pretty expensive. But if the opponent has no CC and you can stall until you have 3 of each out, it might be profitable...
All immaterial creatures (mutants, immortals, phase dragons) have "immaterial" written under them, so I was just trying to emphasize that immaterial would not be written under the creature...Although I just checked Chimera and although both the Momentum and Gravity Pull icons are on him, he has no active skill and his only passive skill is "chimera." Therefore, I will change the notes and my idea of Reaper into the likeness of Chimera: there will be the
Immaterial icon when it is played, but its only passive skill will be airborne.
As for the card text, I will remove the line break to create more space and change the wording into the likeness of all the other healing cards in the game "...Heal yourself for up to..." It may be noted that it would be known that Reaper wouldn't be healed because in every card in which the creature does something, the creature is name i.e. "...Vulture gains...", "boneyard generates...", etc.
I just hope that the mechanic isn't as complicated as the congested card text suggests.
Thanks for replying, these changes will definitely make the card better ^^