As an additional cost to cast this spell, discard X cards.
Nahiri's Wrath deals damage equal to the total mana value of the discarded cards to each of up to X target creatures and/or planeswalkers.
If you cast Nahiri’s Wrath without paying its mana cost, you’ll still choose a value for X and discard X cards.
If you copy Nahiri’s Wrath, it has the same number of targets and deals the same amount of damage as the original spell.
If you discard a card with {X} in its mana cost, X is considered to be 0.
Nahiri’s Wrath adds the converted mana costs of the discarded cards in whatever zone they were put into as a result of being discarded, even if they weren’t put into a graveyard (due to madness, for example) or are no longer in that zone.
The damage is not divided. Nahiri’s Wrath will deal that much damage to each target.
You can’t target the same creature or planeswalker multiple times to deal more damage to it.