Starlit Soothsayer

The lifegain-or-lifeloss condition looks like a tax on the surveil until you count how routinely a black deck moves its own life total: fetch-style pain, drain effects, small lifelinkers, painful mana. The gate is not a hoop so much as a description of what an aristocrats or lifegain shell already does every turn, and that is what pays for stapling repeatable graveyard-filling and card-smoothing onto an evasive body at this rate. An unconditional version would have to cost more or select less. The end-step timing does real work too: the surveil resolves after combat and after most of the turn's life-total math has settled, so it reads the whole turn rather than a single moment, letting you bin a card you no longer want once you have seen how things played out. As a two-power flier it clocks the opponent while the trigger quietly feeds a graveyard for delve, flashback, reanimation, or delirium. This is a glue piece: forgettable in a vacuum, a genuine engine the instant your deck is already spending and gaining life on purpose.