Stern Mentor

Soulbond does the work here, and the whole card is a study in conditionality: the mill ability exists only while the link holds, and when it triggers on entry it arms not one outlet but two, granting the tap ability to both creatures in the pair at once. That is the engine. Pair on entry and a single trigger sets up two repeatable mill sources, each untargeted by graveyard hate and aimed at any player you choose; with both creatures untapped, the duo churns four cards per turn cycle and compounds across turns rather than resolutions. The ceiling is fixed by the mechanic itself, since soulbond links exactly two creatures and the mill never widens past that pairing no matter how large the board grows. The link is also the fragility: lose either creature and the second reverts to whatever it was, both outlets carry tap symbols that fold to the same removal or tapper any attacker would face, and the clock asks you to protect two bodies rather than one. This is mill as an incremental machine, the patient counterpart to one-shot library-emptying spells like Glimpse the Unthinkable: it trades the burst of a single cast that strips a chunk of the deck for a grind that has to survive a turn cycle to pay off, and it does nothing to an opponent who simply ignores the cards going to their graveyard.