Restless Ridgeline

Restless Ridgeline enters tapped.
{T}: Add {R} or {G}.
{2}{R}{G}: Restless Ridgeline becomes a 3/4 red and green Dinosaur creature until end of turn. It's still a land.
Whenever Restless Ridgeline attacks, another target attacking creature gets +2/+0 until end of turn. Untap that creature.

The Lost Caverns of Ixalan Promos

The Lost Caverns of Ixalan

Restless Ridgeline enters the battlefield tapped.
{T}: Add {R} or {G}.
{2}{R}{G}: Restless Ridgeline becomes a 3/4 red and green Dinosaur creature until end of turn. It's still a land.
Whenever Restless Ridgeline attacks, another target attacking creature gets +2/+0 until end of turn. Untap that creature.

If this becomes a creature because of an effect other than its own ability, its last ability will still trigger whenever it attacks.

If this becomes a creature but you haven't controlled it continuously since your most recent turn began, you won't be able to activate its mana ability or attack with it that turn.