Horn Of Plague

Whenever an opponents land is destroyed, they
lose 2 life.
Whenever a creature dies, distribute two -1/-1 counters among any number of creatures.
Whenever a land is exerted, destroy it.
{g}{b}: Until the end of the next turn, target land
loses all other abilities and has "{t}, add {c} to your
mana pool" and "Exert: Add one mana of any color."