Kithkin Shielddare
The pump activation only fires on a blocking creature, which makes this a defensive specialist wearing combat-trick clothing. The restriction is the whole point: you cannot use it to shove an attacker through, only to win a fight you have already chosen to enter, so the card's value rises and falls with how often you are the one being attacked. Because the ability taps a permanent rather than spending itself, the same source ambushes attacker after attacker as long as it survives and you can pay the white. A 1/1 swinging to 3/3 on defense profitably eats a 2/2 and lives, then resets for another white mana next combat, turning a flimsy body into a recurring toll on the ground. That repeatability is the design idea that separates it from one-shot pump spells, which trade themselves for a single tempo swing and are gone. Flexibility comes at a steep price on offense: the body contributes almost nothing when you are the aggressor, and it dies to nearly anything. This is a small utility creature built to anchor a slower white plan, wanting spare mana, a ground stall, and combats you are content to sit back and win rather than push.
