Stormscape Familiar

One of five cost-reducers built to push its block's gold-card themes, each Familiar cutting a generic mana from spells in two of the five colors. This one slants white and black, which makes it an engine for the removal-and-attrition lane: a Familiar on turn two turns the four-mana wraths, the targeted disruption, and the expensive black bombs into plays that come a turn early or stack two-deep. The discount applies on cast, so it compounds across a turn rather than once per game, and it never touches your purely blue spells, which keeps the card honest in a way a flat "spells cost less" would not. The body is the tell about where it belongs: a 1/1 flyer chips in over the top of the ground stalls that grindy white-black decks tend to build, but it folds to any removal aimed at it, so the discount is real only as long as the Familiar survives. That fragility is the whole bargain. You pay two mana up front for an evasive body that contributes little pressure on its own, and you ask the opponent whether spending a card to kill a 1/1 is worth shutting off your tempo. The line of cost-reducing two-drops it belongs to has been redrawn many times since, but the structural idea (a cheap, killable enabler that only rewards a deck genuinely committed to two specific colors) is exactly the constraint that keeps these effects from warping a format.