Reito Sentinel

A Defender that mills three on arrival and then buys back single cards from any graveyard for three mana is a construct with two jobs pointed in opposite directions. The entry trigger fills a graveyard; the activated ability empties one, tucking a card to the bottom of a library rather than exiling it. That distinction matters: bottoming is a softer answer than exile, a way to reset a graveyard resource or deny a specific recursion target without shutting the strategy off, and it hits any graveyard, so the same body can feed your own bin and dismantle an opponent's. The three-mana repeatable cost keeps the ability honest as a slow grind tool rather than a hard lock; you are paying full price every time you want to reach in and rearrange what is dead. The mill trigger is the wrinkle, since it targets any player and can be pointed at yourself when a stocked graveyard is the plan or at an opponent when it is a clock. Behind a 3/3 body that cannot attack, the design settles into a defensive support piece: a wall that also does graveyard maintenance, built for decks that treat the yard as a battlefield of its own and want a durable, repeatable way to tend it.