Obsidian Obelisk

The design question here is how to hand a multicolored deck fixing without also handing every deck in the format two-mana ramp. The answer is a split personality: the second ability produces one mana of any color, but that mana is walled off to multicolored spells only, while the colorless it makes is unrestricted. That restriction is the whole balance. A gold-heavy deck reads this as flexible color correction that also chips in generic mana; a two-color goodstuff pile that runs plenty of monocolored spells finds the flexible half of the rock frequently dead. It enters tapped, so the ramp it offers is deferred rather than explosive, which keeps it out of the fast-mana conversation entirely. The lineage runs through the long line of color-fixing rocks that tried to price the "any color" upside behind a usage clause rather than a higher cost, and this lands on the strict end of that spectrum: cheap to cast, narrow in what its best mana can pay for. It rewards a specific kind of deckbuilding discipline, where the density of gold cards is high enough that the conditional mana rarely goes to waste, and punishes the reflex to jam any two-color ramp piece into any two-color list.