Willowdusk, Essence Seer

The clever pivot is the "whichever is greater" clause, which lets one card sit at the head of two opposite strategies. Lifegain and life-loss are usually antagonistic axes: soaring to a towering total off a chain of lifegain triggers pulls in a different direction than hemorrhaging your total to power Necropotence or Bolas's Citadel, and each leans on a different card pool. This routes either direction into raw stats, so a Golgari build can commit to gaining hard or bleeding for card advantage and feed both outcomes through the same counter engine. Crucially, the two amounts are tracked independently and cumulatively across the turn, not netted against each other: gain ten and lose ten in the same turn and you still hand out ten counters, because the ability reads whichever total is larger, not the difference between them. That also means it counts aggregate gains or losses however assembled: ten instances of one life or a single ten-life swing both come out to ten. The sorcery-speed restriction keeps the counter dump on your own turn, making this a proactive threat-builder rather than a combat-speed reactor, and the tap cost means one target per turn absent untap tricks. It quietly rewards the pilot for maximizing the life swing before the ability resolves, since only what has resolved this turn counts. What you build around Willowdusk is less a specific creature than the shape of your life total's volatility: the more violently it moves in either direction, the larger the body it hands whatever you point it at.