Serpentine Ambush [Innistrad: Double Feature] BW20 and beyond that was a

and beyond that was a light on the sky that spoke of the Sea

and "{1}: This creature gets +1/+0 until end of turn

Set: Unknown Event Type: Sorcery Rarity: Common Cost: {1}{U} Choose One —

Set: Double Masters 2022 Type: Creature — Kithkin Rarity: Rare Cost: {R/W} {R/W}: Figure of Destiny becomes a Kithkin Spirit with base power and toughness 2/2

but I believe a more mundane power source might suffice

Serpentine Ambush [Innistrad: Double Feature] BW20 and beyond that was aSet: Innistrad: Double Feature Type: Instant Rarity: Common Cost: {1}{U} Until end of turn, target creature becomes a blue Serpent with base power and toughness 5 5. The merchant did guarantee the new bait would bring in something big.