I think it's a great idea for a card, and keeping the effect occurence to when attacks are successful looks like it would nerf it well, but I'm not sure if it needs that. I'm guessing it doesn't lobo the creature and replace ability with hex? That would present more strengths and weaknesses for use.
Thanks for the feedback!
That's another great idea. I guess I'd need to raise the cost, again. I rather imagined that Hex would have a counter, just like Poison.
Making it a skill (like Overdrive) would add the weaknesses that it could be removed with Lobotomise and it would not stack.
On the other hand, it would also lobotomise the opponent.
I have to reconsider, but I think the counter version is better. I'd cast this spell on Dragons and similar creatures, which often don't even have skills, so the skill addition is unnecessary, so only the drawbacks would be significant.
I'll think about it, though. Maybe the unupgraded version should add it as skill and the upgraded one would add it as a counter?