Sejiri Merfolk

The conditional is the whole design: a 2/1 in mono-blue that sharpens into a 2/1 with first strike and lifelink the moment you control a Plains, which on a two-power body means trading up in combat and clawing back life every time it connects. The mechanism rewards a land type rather than a color of mana, so a single Plains (or a dual with the Plains subtype) flips the static ability with no deeper white commitment. That keeps the card mono-blue on the spell side while quietly rewarding an Azorius manabase: the body stays a single-color blue creature, but the printed enhancement only ever arrives through the partner's land. The result is an aggressive blue beater that punches into ground stalls, since first strike turns a fragile 2/1 into a creature that survives blocking most early bodies, while the lifelink offsets the chip damage of a race. It belongs to an early-era approach to allied-color encouragement: a single-color creature that graduates from filler to playable when its partner land type shows up, nudging two-color builds without diluting the card's color identity or asking for a second mana symbol on the spell. Naked, it is a forgettable two-drop; given the one land it asks for, it does honest work for the cost.