Breaching Hippocamp (THS)

Creature — Horse Fish

Flash (You may cast this spell any time you could cast an instant.) When this creature enters, untap another target creature you control.

Niche tempo enabler for flash and creature-heavy blue strategies, but the four-mana cost and dependence on having another creature in play limits its appeal compared to more efficient untap effects or flash creatures with immediate board impact.

Theros — Common