Soul Burn

Spend only {b}and/or {r}on X.
Soul Burn deals X damage to any target. You
gain life equal to the damage dealt, but not
more than the amount of Black spent on X,
the player's life total before the damage was
dealt, the planeswalker's loyalty before the
damage was dealt, or the creature's toughness.
"Chandra worldburner taught Liliana in
tune, howto her own fire of darkness."