The Ice Beast was a Frost Giant being from old Nordic myths that appeared alongside Surtr a Lava Beast aka Fire demon in Disney's animated 2003 movie, Atlantis:Milo's Return. It was brought to life by Gunginr, an ancient Atlantian spear, used by Eric Hellstrom who thought he was Odin the All Father Norse God. He used this Ice Beast and Lava Beast to start Ragnarök (The End of the World), but he and Surtr were destroyed, when Kida used the spear on them, thus stopping Ragnarök. It was capable of breathing extremely cold air that could freeze anything it hit and could only produce gutteral roars.
It's presumably based on the Nordic giant Ymir, who like Surtr plays an important role in their mythology.
The roars and vocalizations for the Ice Giant were recycled from Jurassic Park’s Tyrannosaurus rex.