Teval, Arbiter of Virtue

Flying, lifelink
Spells you cast have delve. (Each card you exile from your graveyard while casting those spells pays for {1}.)
Whenever you cast a spell, you lose life equal to its mana value.

Tarkir: Dragonstorm Promos

Tarkir: Dragonstorm

Flying, lifelink
Spells you cast have delve.
Whenever you cast a spell, you lose life equal to its mana value.

If a spell on the stack has an {X} in its mana cost, use the value of X chosen as it was cast to determine that spell’s mana value.

“Delve” means “For each generic mana in this spell’s total cost, you may exile a card from your graveyard rather than pay that mana.” The delve ability isn’t an additional or alternative cost and applies only after the total cost of the spell with delve is determined.