Frost Wyrm is a dragon boss. At the lowest Threat it has 1050 health, hits for 22 and carries 6 armor; the uber version you meet in the Mortal Arena has ×1.6 the health and ×1.75 the damage. You need Frostwyrm Fang to call it out.

It waits at the end of Frostmere Reach, in place of Imp Overlord, and belongs to Adventure Mode.

Every kill rolls its list 5 times. 8 Uniques sit on it: four ordinary ones splitting 90.0% of it between them, and four Exceptional ones splitting the last 10.0%, which puts any one of those at about 1 in 40 of what it gives up. The Exceptional ones are The Glacier's Patience, A Hundred Winters, Solstice Vigil and The Long Slide.

It opens every fight with Glacial Breath, then fights with Whiteout Wing and Shard Spiral. The cast bar under its health names each big move as it winds up, so a party can call them out to each other. At 60% health it changes phase with Beneath the Ice into The Long Winter. After each big set piece it stops for a breath: that is the opening to punish. At 15% it makes its Last Stand with Absolute Zero, one named, fully telegraphed finisher, and no burst of damage skips it. The uber version in the Mortal Arena fights in three phases (Rime, Whiteout and Absolute Cold), grows between them, and adds Frozen Tomb and Avalanche. Its weak spot: Light the Braziers. Stand at each brazier to light it: with every fire burning, the Wyrm lands on thawed ice.

It calls in Frost Whelp.