Triple Helix

(You can only cast a legendary instant if you control a legendary creature or planeswalker)
This spell cannot be countered, and damage dealt
to your opponents this turn cannot be prevented.
You gain three life. Draw three cards, then
add {b}{b}{b}. Triple Helix deals 3 damage
to any target, then up to one target
creature gets +3/+3 until the end of turn.