This is probably one of the more confusing cards Ive seen in a while
While this effect can only trigger off of each of your opponents once per turn without the use of additional combat phases or double strike, Breeches provides a great payoff for going wide with your Pirates, providing card advantage in the form of your opponents' own cards
This can be an excellent mana sink with some +1/+1 counter creatures
A creature with 0 power can attack, as long as it doesn't also have defender
So, if the attacking creature's strength overpowers the defending creature's toughness, and the defending creature's strength overpowers the attacking creature's toughness, both creatures die
This means you'd have to use the +1 four times, without losing any loyalty, to build up to this