Awesome.
I like the Avosion ability but still questionable on how it would work in the game. If you play a firebolt against the Ghost, would it:
A: Prevent the targeting in the first place. Which poses the problem that the user will just cancel the Spell and be able to try again until the chance fails.
B: After being selected as a target give a chance to simply negate the effects. Which makes it very effective at breaking card advantage as the user has to waste the card just in the attempt to try and clear the target and might not succeed.
Immaterial creatures don't create this situation as its simply all or nothing.
Actually while writing this I have just thought of a solution.
Use option A, but the Avoision chance is rolled on the creatures action making the card immaterial until the next time the roll is made. Immaterial creatures now will get a 100% roll, avoision creatures will have a lower % roll.