Resolve the first Retreat to Coralhelm trigger, causing you to either tap or untap a creature, or scry 1.
Resolve the second Retreat to Coralhelm trigger, untapping Sakura-Tribe Scout.
Activate Mina and Denn by paying ({R} magic symbol) ({G} magic symbol) and returning the land from the battlefield to your hand, giving target creature trample until end of turn.