Rune of Protection: Blue

The cycle of color-hosers that solved the dead-draw problem. Protection circles had existed since Alpha (CircleOfProtection: Blue and its siblings), but a circle drawn against a deck that never appeared just sat in your hand as a blank, the worst kind of reactive card: insurance you paid for and never used. Urza's Saga's runes answered that with cycling, the keyword that debuted in the same block. The repeatable damage-prevention activation is the same insurance the old circles sold, but the -and-discard line turns the dead matchup into a fresh card. That is the whole design idea: a sideboard card that costs you nothing when it is wrong. The prevention itself works one source at a time per activation, so it taxes your white mana to keep ahead of multiple threats rather than locking out a color wholesale, and it does nothing against noncombat losses or non-blue damage. But the structural innovation was never the prevention rate; it was attaching an escape hatch to a narrow hate piece so that drawing it in the wrong game stopped being a punishment. Every flexible sideboard card that since came stapled to a cantrip or a cycling cost owes something to this idea.