Chronic Concussion

Enchant player
Convoke, dredge 3
When enchanted player takes damage, put X pain counters on Chronic Concussion, where X is the amount of damage taken.
{u/r}, Remove Y pain counters from Chronic Concussion: Counter target spell controlled by enchanted player. (Y is 8 minus the target spell's converted mana cost.)
Remove 1 pain counter from Chronic Concussion: Regenerate Chronic Concussion.