Eye of Ugin

Cost reduction printed onto a land is an effect that scales without ever costing a card to play, and this one targets a creature family whose top end is measured in tens of mana. The legend rule caps you at one in play, so the discount does not stack; the breakage comes from how cheaply and reliably the static line gets online and how indifferent the discount is to everything around it. Shaving two off every colorless Eldrazi spell, unconditionally and repeatably, off a permanent that does not even need to tap for the mana it discounts, lets a deck cast a colossal threat well ahead of its printed curve and keep doing it. The seven-mana tutor is almost a footnote, a slow toolbox for any colorless creature, but the static line is the whole reason the card exists and the reason it eventually broke. Land-fetch and fast colorless mana let an Eldrazi-aggro shell find it and back it, turning the giant Eldrazi from a fair late-game payoff into a clock. That acceleration is what got it banned in Modern, where the decks built around it were warping the format inside a single season. Stripped of context, the design reads as a cautionary case in mana acceleration hidden on a permanent that pays no cost to provide it: the kind of discount that looks tame at one copy and indefensible the moment a deck is assembled to exploit it.