Blood Feud

A spell or ability may instruct a creature to fight another creature or it may instruct two creatures to fight each other. Each of those creatures deals damage equal to its power to the other creature.

If one or both creatures instructed to fight are no longer on the battlefield or are no longer creatures, neither of them fights or deals damage. If one or both creatures are illegal targets for a resolving spell or ability that instructs them to fight, neither of them fights or deals damage.

If a creature fights itself, it deals damage to itself equal to twice its power.

The damage dealt when a creature fights isn’t combat damage.