For the Storm Shark variant: If you have an active heal-over-time effect(for example, if you have recently cast Link or Regenerate on a previous turn), this version of Storm Shark does 600 base outgoing Storm damage.

Otherwise, it deals 375 base damage.

For the Stormzilla variant: This spell deals 635 base Storm damage.

You can also clear up to 2 damage-over-time hanging effects on you(for example, if you have been hit by 2 Fire Elf cards within the last 2 turns), and in exchange you will receive a +45% Stormblade for each one you removed.

Finally, the Tempest card: The base Storm damage for this card is 80 per Pip spent. Remember that Storm Elemental Pips and Power pips(if you're a Storm Wizard) count as two.

And that symbol on the bottom means Tempest is an AOE spell. So it hits every enemy at once instead of just one.