Grasping Dunes

A colorless source that taps for one and later cashes itself in for a kill once the mana no longer matters. What kind of kill matters here: shrinking a creature's toughness with a permanent counter, not dealing damage, so the reduction sticks, ignores indestructible, and stacks with any other plan built on shaving stats rather than burning them off. The sorcery-speed restriction is the cost. You cannot hold this up as a combat trick; you commit to the kill on your own turn, with the land already headed to the graveyard. That sacrifice clause is the harder tax, because the ability demands you give up this exact land, not any other Desert you control: every activation thins your manabase by a source, so the design asks you to bank the colorless early and spend the land late, once an extra source matters less than a dead one-toughness creature. The permanent shrink also ties it to a specific attrition vocabulary, the wither-and-persist family where bodies die by getting smaller rather than by taking damage. As a land that draws no card and demands a full mana investment plus its own life to fire, it is deliberately marginal: interaction you tuck into a slot that was already going to hold a colorless source, free only because the land was going in anyway.