Undermine

+1: Target permanent doesn't untap during its controller's next untap step. −2: Ajani deals 3 damage to any target and you gain 3 life. −7: Destroy all lands target player controls.

This creature gets +1/+2 as long as you control a Forest.

Whenever another creature enters, you gain 1 life.

This creature gets +1/+1 as long as you control a Mountain. This creature gets +1/+1 as long as you control a Plains.

This creature gets +1/+2 as long as you control a Forest.

Mountainwalk (This creature can't be blocked as long as defending player controls a Mountain.)

(T: Add R.)

2G: Create a 1/1 green Saproling creature token.