Thrym

Thrym is the boss of Thrymheim, an inverted ice-pyramid dungeon in ALfheim Online, and the central antagonist of the Calibur side story. Generated by the Cardinal System's Automatic Quest Generation function and modeled on the king of the frost giants from Norse mythology, he possesses far greater intelligence than an ordinary NPC, able to adapt his speech naturally rather than relying on scripted responses.

In the game's lore, Thrym infiltrates Jötunheimr disguised as a wolf, steals the Holy Sword Excalibur, and casts it into a sacred spring, severing the roots of the World Tree and turning the realm into a frozen wasteland. From his fortress at Thrymheim he rules the frost giants, imprisons the native rock giants, and hunts the beasts that once protected the realm, all while working to reach the top of the World Tree for the fabled Golden Apple — kept in check only by the guardian sisters Urd, Verðandi, and Skuld. Visibly displaying three separate health bars unlike other floor bosses, he is ultimately defeated when Kirito's party frees the disguised Thor from his cage and helps him reclaim his hammer.