Dragon's Claw

Color hate sold cheap and colorless, so any deck could install it as a wall against a single enemy. The trigger keys off the cast, not the spell resolving or dealing damage, which is the whole structural point: each red spell your opponent commits to the stack repays you a point whether it lands, gets countered, or fizzles. Against a deck trying to race your life total to zero, that math quietly bends the wrong way for the aggressor. Every Lightning Bolt, every cantrip, every burn spell aimed at your face now buys back a fraction of clock just by being announced, and over a long game those single points accumulate faster than a red deck wants to admit. It touches neither the board nor the clock; it is purely defensive insurance, paid for in two generic mana. It belongs to a colored set of these watchmen, each tuned to punish one color's spell-heavy aggression, and the red one earned the most reputation because red is the color most willing to convert its hand directly into damage. The lifegain is technically symmetric (your own red spells trigger it too), but nobody assembles a deck to exploit that; this is something you put up against someone else's plan, not something you build around.