Mohgwyn's Sacred Spear

{p/r}{p/r} Attach Mohgwyn's Sacred Spear to a creature.
{p/r}{p/r}{p/r}{p/r} All creatures take damage in the
form of -1/1 counters. Each time this spell is cast, add 1 blood counter to Mohgwyn's Sacred Spear. Once 5 blood counters are reached, remove 5 blood counters and all
opponents take 5 damage.