Not strict: River of Tears has a lot going for it
There are enough payoffs for stocking your graveyard with lands, including Crucible of Worlds, Splendid Reclamation, and Cavalier of Flame, that a land-discard strategy isnt unplayable, though it might be niche
Eldrazi Obligator can fill your curve in the two drop slot, or you can hold it to surprise your opponent by stealing a blocker and attacking for a bunch of unexpected damage
Other prominent mechanics that incorporate (or freely enable) sacrifice include: Food, Clues, Treasures, Sagas, Unearth, Encore, Evoke, any other temporary tokens such as Faerie Artisans or Hostility, cards with Upkeep, Quests, Exploit, Casualty and now Bargain
Many vatkeepers use necrogen etchings to judge the value of their aspirants
27 Description Specs Reviews Find in Store Features Explore the depths for lands and buff your army of Merfolk to change the tide of battle