Norn's Wellspring

One death trigger, two effects, and the split between them is the whole design. Every creature death both scries and banks an oil counter, so the free half (the scry) fires immediately while the value half is deliberately deferred: two counters buy one draw, and that draw still costs a mana and a tap on top. The gearing is the point. Feed the artifact a dozen deaths in a turn and it converts them at exactly half speed, spending its reservoir down only when the extra card actually matters and leaving the scry to smooth your draws the rest of the time. That converting-reservoir approach does the structural work that older sacrifice payoffs handled with a fixed threshold or a hard per-turn cap: instead of a ceiling, you get a bank that fills and drains at your discretion. It descends from the "creatures die, cards flow" impulse of Skullclamp and its kin, but stripped of the burst that gets those cards banned and retuned into a grind engine. The scry is what keeps that grind from stalling: each death lets you shape the top of your library before the next draw arrives. Built for the long game rather than the explosive one, it rewards a sacrifice loop that keeps running well past the point where a faster engine would have either closed the game or run out of gas.