Frost Wyrm

Boss phases

A frozen lake below the peaks at Night with Aurora, switching to Blizzard in phase 3. The aurora flickers brighter just before each breath attack as a second telegraph (the "sky warns you" beat). An ice spire stands at x = 1300.

1. "Sky Dance" (100–60%). It flies figure-eights across the upper field. It can only be hit by fliers' counters (archers, crossbow, storm, and fire bolts). Frost Breath: telegraph its throat glows blue with a big inhale (1.5 s) and a dotted cone on the wall. Effect: a sweep that freezes one defender tower slot for 4 s (the defender turns into an ice cube) and slows marching units 50% for 3 s. Boiling Oil or Pyromancer adjacent to the frozen slot thaws it in 1 s.
2. "Perched" (60–25%). It lands on the ice spire and becomes grounded, so catapult and melee can hit it. Its chest crystal glows as a weak point (hits there do ×1.5). Tail Sweep: telegraph the tail rattles (0.8 s), then it knocks back all units within 250 px. It cries icicles that turn into 4 Snow Imp every 12 s.
3. "Blizzard" (under 25%). It takes off and the weather switches to Blizzard, with strong wind that's shown in the arc preview. Icicle Rain: 5 shadow circles on the wall/field (a 1 s telegraph), then icicles fall (6 damage each, and they briefly stun units). It breathes every 7 s.

How to beat Frost Wyrm

Crossbow (++, bolts hit fliers and bolts are wind-stable), Pyromancer (icy +50%), Balcony Archers (compensate for wind), Boiling Oil to thaw, and Pikeman/Keep Catapult during the perch. Cryomancer shows "resist".

Best counters: Crossbow Tower and Pyromancer.

Also works: Balcony Archers, Stormcaller, Pikeman and Ranger.

Not great against it: Cryomancer.

• It is a boss with three phases. Watch for the big warning signs before each attack.
• It flies, so marching troops cannot reach it. Archers, crossbows, storm magic, and rangers can.
• Icy foes take 50% more fire damage and shrug off frost.

Frost Wyrm in the campaign

On Normal you'll face one Frost Wyrm over 1 day, spread across 1 wave. Harder difficulty levels send more of them, with more health; Easy sends fewer.

What it looks like

A long serpentine dragon in ice-blue and white, with frosted pink wing membranes (alpenglow), a fringe of icicles like a beard, and big sleepy-grumpy eyes. The chest crystal is a glowing snowflake. Gag: when its breath is interrupted (it takes 50 damage during the inhale) it sneezes instead, and the breath fizzles into harmless snowflakes. That's a hidden skill reward.

The elite version

"Twin Breath": in phase 3 its breath freezes 2 slots.

Similar enemies

• Ice Golem
• Snow Imp
• Yeti
• Big Bruno, Ogre Chief

See every foe in the enemy almanac, or read the Day 18 walkthrough.