Walrein is a large, sea lion-like Pokémon with a layer of blubber under its skin. It is primarily blue, with thin, white rings around its neck and lines on its fan-like tailfin. There are two long, ivory tusks in its upper jaw. It has a round snout and yellow eyes, and large tufts of white fur about its face and neck. Its four short legs have long flippers instead of feet.
Walrein lives in and around icy seas, where it is insulated against the cold by its thick layer of blubber. This layer of fat also protects it from enemy attacks by causing them to bounce off. It can coat its body in ice and charge opponents to use its former signature move, Ice Ball. While its long tusks are capable of crushing ice, they may break during battle. This Pokémon can be found in herds, which are fiercely protected by the leader.
A Walrein appeared inTraining Wrecks, under the ownership of Rocky, who had a battle with Ash. Walrein battled Pikachu and Grovyle, alongside a Quagsire. Before Grovyle could attack Quagsire with its Leaf Blade, Walrein attacked Grovyle with its Ice Ball. Pikachu defeated Walrein in the end, while Grovyle took care of Quagsire.
A Walrein was Katie's final Pokémon during her battle with Ash in A Judgment Brawl. The Ice Break Pokémon defeated Swellow and Corphish (the latter of whom was already tired out from battling Katie's Golduck), and was defeated by Ash's Grovyle.
Walrein first appears in Walrein and Camerupt. He was used by Archie to battle against Maxie, and later when ironically fighting alongside the Magma Leader against Ruby and Sapphire, though they are able to exploit the two leader's weakness of taking little notice of each other's presence and easily won. A few more volumes later, in the climax of the Ruby & Sapphire chapter, Archie sends out several more Walrein alongside Maxie's multiple Houndoom to buy time for the two to escape, but are thwarted.