Kamahl's Druidic Vow

The X-on-both-ends structure is the whole bet here: every point poured in raises both the dig depth and the mana-value ceiling on what you can put onto the battlefield off the top. That coupling is what separates it from ordinary green ramp. A typical put-lands-into-play spell scales in one dimension; this one scales in two at once, so the payoff curve bends sharply upward when the deck is built around high-cost legends. The catch is written into the type line: as a legendary sorcery, it demands you already have a legend on the board (and specifically a creature or a planeswalker, since a legendary artifact, enchantment, or land will not grant permission), so you have to earn the right to fire it. Once it is on the stack the enabler can vanish and the spell still resolves; the tax is on the cast, not the resolution. Equally important is what does not get hit: anything that is neither a land nor a legendary permanent card with mana value X or less goes straight to the graveyard, so the dig is loud and lossy rather than a gentle Impulse-style peek. It rewards a deckbuilding posture, not a single clever turn: lean hard on lands and singleton legendary permanents, and a large X becomes a board state that smaller incremental ramp simply cannot replicate in one cast.