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You're talking about the Deep Leviathan.

You can read more about this pet via wizard101central.com:

http://www.wizard101central.com/wiki/Pet:Deep_Leviathan

Storm wizards gain access to this pet at level 78, visit the little frog storm professor for the quest.

I have a couple of Deep Leviathan pets:

(Mega) Deep Leviathan, Fluffy 65 (30) Storm Blade, Disarm and Leviathan Cards, May cast "Fairy", +22 Storm Critical Rating, May cast "Healing Current", May cast "Tower Shield"

(Adult) Deep Leviathan, Sammy 63 (12) Storm Blade, Disarm Cards, May cast Stormspear, May cast "Tower Shield"

Other storm pets I have:

(Mega) Li'L Siren 57 (32) Gives 3 Sirens Cards, +9% All Resistance, +7% Outgoing healing, May cast Pierce, +6% Storm Damage, May cast Sprite

(Mega) Li'l Siren 58 (24) Gives 3 Sirens Cards, +9% All Resistance, +6% Storm Damage, May cast Sprite, Healing Current, and Fairy

(Ancient) Triton 54 (17) Royal Triton and Disarm Cards, +5% Storm Accuracy, +6% Storm Damage

(Ancient) Kraken 59 (17) Gives 1 Berzerk Kraken Card, +4% Storm Accuracy, may cast Sprite and Stormblade

(Ancient) Frankenbunny 51 (18) Gives 2 Healing Current Cards, +2% Outgoing health, +15 Critical Rating, May cast Healing Current

(Ancient) Cloud Demon 53 (14) Kraken Card, +4% Storm Accuracy

(Adult) Toaddle 59 (12) Gives Cleanse Charm and Boss Toad Cards, + 3% Storm Shield

(Adult) Toaddle 62 (20) Gives Cleanse Charm and Boss Toad Cards, May cast Infallible Spell

(Baby) Li'l Siren 65 (0) Gives 1 Sirens Card

I also have a Stormzilla and storm dog (I forget the pet type) at my houses.

Let me know if you want to hatch with any of these pets, or any of my other pets with many other talents.