Shell Skulkin

Color-pinned protection is one of the stranger micro-mechanics in design, and this Scarecrow is built entirely around it: a colorless body that pays three mana not to protect itself but to throw shroud onto a blue creature, anyone's blue creature, for the turn. The restriction is the whole shape of the thing. The activation is repeatable and instant-speed, so it answers targeted removal and aura-style trickery in the window where they go on the stack, but it can only ever cover a blue target, which fences it to a single color identity rather than a general bodyguard. That narrowness is the cost of the rate: a cheap, recurring shroud-granter would warp protection math badly if it worked on any creature, so the design buys back its flexibility by demanding the right color be on the board. The 3/2 frame is incidental; the card is really a colorless permission slip that happens to come attached to a fragile attacker, a deliberate piece of color-matters engineering aimed at a blue-creature shell that wants its threats to survive the turn they matter.