Emerald Nightmare

({t}: Add {u}, {b}, {r} or {g} to your mana pool)
Whenever Emerald Nightmare gets tapped for
mana, you lose 1 life for each creature you
control and gets a poison counter.
"To see Yogg-Saron's nightmare in full bloom fills me
with jealousy...and a bit of pride."
—Xal'atath