Darigaaz's Caldera

A free land that taps for three colors, with the catch buried in its entry trigger: unless you return a non-Lair land you control to your hand, this hits the graveyard immediately. The math comes out to a tempo loss now (you are effectively down a land drop) in exchange for a fixed Jund source the rest of the game, which is why this whole cycle of Lairs reads as a beating up front that smooths out after rather than a ramp piece. The constraint that keeps it from being abusive is the single word non-Lair: you cannot chain one Lair into another or bounce-and-replay the same Caldera for value. Strip that word out and this becomes a recursion engine instead of a one-time fixer. For these three colors specifically, it predates the modern glut of dual and tri-lands that enter untapped, landing in an era when smooth black-red-green fixing was a genuine luxury and giving up a land felt like a fair price. The mandatory return is not pure downside in a vacuum: it can re-trigger an enters-the-battlefield land or pull a threatened permanent clear of removal, but those are corner cases the design never leaned on. What it was built around is clean Jund fixing for a time when fixing was scarce and the tempo hit was a price worth paying.