If a source you control would deal damage to an opponent, prevent that damage and each opponent mills that many cards.
Win by milling all opponents out rather than dealing damage. The Mindskinner is a cheap, unblockable evasive body that connects every turn, and its damage-to-mill replacement turns your whole board and any 'damage to opponents' effects into mill engines. Build a mono-blue mill deck supported by pingers, X-spells, and direct-mill payoffs, then close with a big mill burst or by exhausting every library.
Converts all damage you deal into mill, so burn, pingers, and combat damage become library destruction across all opponents
Unblockable on a 3-mana body that mills consistently every combat
Mono-blue gives access to the deepest pool of mill, card draw, counterspells, and protection
Damage-to-mill conversion scales explosively with high-power creatures, X burn, and group-wide ping effects
Slow primary win condition that gives opponents time to assemble graveyard payoffs
Helps graveyard/reanimator and 'whenever a card is milled' decks, sometimes filling their yards for free
Legendary Enchantment Creature — Nightmare
