Join Forces⁣ - Dominaria United⁣ (Uncommon)⁣ [21]

Join Forces is an instant spell that allows you to untap up to two target creatures, giving them a temporary boost of +2/+2 until the end of your turn. You’d want to play this card in situations where you need to swing for a game-ending attack or defend against an incoming threat, as it can surprise your opponent by allowing creatures to block or attack that were previously tapped. However, it’s crucial to note that the effect is temporary, so it's best used when you can make a significant impact immediately, and it won't help if your opponent has removal spells waiting.