This clever loop transforms Walking Ballista into a self-sustaining engine by leveraging replacement effects to generate more resources than it consumes. When you activate Walking Ballista to ping itself, Angrath's Marauders steps in to double that damage output, which Vigor then redirects into a generous bounty of +1/+1 counters rather than lethal harm. Because Vigor replaces the damage with twice as many counters as you removed to pay the cost, Walking Ballista actually grows larger with every single iteration instead of dwindling down. This lets you endlessly repeat the process to churn out arbitrarily large creatures, and once your counters are infinite, you can simply redirect that final salvo of damage straight at an opponent's face to close out the game.