Mohgwyn's Sacred Spear

{p/r}{p/r} Attach Mohgwyn's Sacred Spear to a creature.
{t}{p/r}{p/r}{p/r} All creatures except for the attached creature take damage in the form of -1/1 counters. Each time this spell is cast, add 1 blood counter. Once 3 blood counters are reached, remove 3 counters and all opponents take 5 damage.