As an additional cost to cast this spell, discard X cards.
Nahiri's Wrath deals damage equal to the total converted mana cost of the discarded cards to each of up to X target creatures and/or planeswalkers.
7/13/2016 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.
7/13/2016 The damage is not divided. Nahiri’s Wrath will deal that much damage to each target.
7/13/2016 You can’t target the same creature or planeswalker multiple times to deal more damage to it.
7/13/2016 If you discard a card with in its mana cost, X is considered to be 0.
7/13/2016 If you cast Nahiri’s Wrath without paying its mana cost, you’ll still choose a value for X and discard X cards.
7/13/2016 If you copy Nahiri’s Wrath, it has the same number of targets and deals the same amount of damage as the original spell.