Infinite +1/+1 counters on a creatureNear-infinite card draw for target opponentNear-infinite damageNear-infinite draw triggers for target opponentTarget opponent loses the game
How it works
Cast Peer into the Abyss by paying 4, targeting an opponent whose library size is larger than or equal to their life total.
Resolve Peer into the Abyss, causing that opponent to draw cards equal to half their library size and causing them to lose half their life total, rounded up.
Orcish Bowmasters triggers for each card drawn, dealing 1 damage to the opponent for each card drawn this way and putting that many +1/+1 counters on an Army you control.
The opponent loses the game due to having zero or less life.