Arena of Glory - Modern Horizons 3 - 215

Land

This land enters tapped unless you control a Mountain.
{T}: Add {R}.
{R}, {T}, Exert this land: Add {R}{R}. If any of that mana is spent on a creature spell, it gains haste until end of turn. (An exerted permanent won't untap during your next untap step.)

Rare · Modern Horizons 3 · #215 (MH3)

Illustrated by Jorge Jacinto