Safehold Duo

Two triggers, two colors, and a single defensive body waiting to be activated by either one. Cast a green spell and this 2/4 swells for the turn; cast a white spell and it picks up vigilance until end of turn. Apart, neither does much, and both bonuses vanish when the turn ends. Together, on a turn where you sling one of each, they convert a wall into a 3/5 that swings and still holds the ground behind it. The flexible colored pip in the cost is the giveaway about who this was built for: a deck splitting its spells evenly between the two colors, emptying its hand in bursts rather than trickling out one spell per turn. A grindy attrition shell that casts a single mono-colored spell a turn never sees both modes fire, and that is the wager the design makes: it pays out for volume, not patience. It belongs to a small cycle of two-headed creatures that each reward casting in a particular pair of colors, pairing each color's spells with an effect that color naturally cares about (growth for green, staying back for white). This one is the most coherent of the group, because the two triggers point at the same fantasy from opposite ends: green turns it into a threat, white keeps it from having to choose between attacking and defending.