Emerald Weapon

Enrage - Deal 3 damage to all creatures target
opponent controls.
{2}{u}{u}{g}{g}: Deal X damage to all creatures
target opponent controls, where X is the total
number of basic lands that opponent controls.
Target opponent may reduce this damage by
tapping a basic land for every creature they
control. Damage is reduced by 1 for every land
tapped in this way.
Defender of the planet, the watery depths are
its domain.