Ria Ivor, Bane of Bladehold

The combat-step trigger works by inversion: instead of amplifying a creature's damage, it cancels it and pays out in bodies. Point the trigger at your own largest attacker, prevent that creature's damage, and convert every point it would have dealt into a 1/1 Phyrexian Mite with toxic 1. A creature that would have connected for six damage instead spits out six Mites, each carrying poison and none able to gum up the ground on defense. That turns a single big swing into a swarm pressing the poison clock rather than a burst of life loss that resets each turn. Battle cry stacks with the plan cleanly: the tokens it manufactures are attackers next turn, and pumping the converted target adds one more point to the following combat's prevented-damage conversion. The two abilities feed each other in a loop, one building the board the other draws from. The timing is what stops it from reading as a free win: the prevention is chosen at the beginning of combat, before blocks, so you commit to which creature gets converted without knowing whether it would have gotten through. A creature fully blocked without trample deals no combat damage to players and mints nothing. The build wants evasion or trample on the target, or a board wide enough that Battle cry pushes something lethal through regardless of who holds the ground.