Old Mother Hollowbark

Boss phases

A deep-forest clearing at Dusk with Fog and Fireflies. Fireflies drift across and light up silhouettes as they pass, which previews the fog counter. She carries a firefly lantern that lights a 250 px radius around her.

1. "Walking Wood" (100–66%). She shambles forward on root-feet. Every 6 s she plants a row of 3 saplings. Telegraph: her fingers twitch and the ground sparkles green where they'll sprout (1 s).
2. "Rooted" (66–30%, or when she reaches 800 px). She roots in place. Regen of 10 HP/s runs unless she's burning. Root Spikes: a glowing mushroom ring appears under a marching unit (1.2 s telegraph), then roots burst up and toss the unit back to the gate, unharmed but dazed (kid-friendly). She thickens the fog to 45% visibility. Weak point: the lantern. Three arrow hits make her drop it, the lantern shatters into fireflies, and her twig-skirt catches a cartoon fire that halts regen for 8 s. The lantern regrows after 15 s. This is the game's first weak-point lesson.
3. "Uprooted" (under 30%). She tears free and stomps forward at 0.6×. She throws acorn bombs at the wall (a dotted arc and a shadow circle as the telegraph, 12 damage), summons saplings every 4 s, and regen is off.

How to beat Old Mother Hollowbark

Archers (the lantern weak point), Boiling Oil (she eventually reaches the wall in phase 3), Keep Catapult for sapling rows, Pikeman for the giant, and Pyromancer on replays.

Best counters: Boiling Oil and Pyromancer.

Also works: Balcony Archers, Crossbow Tower, Keep Catapult, Stormcaller, Pikeman and Ranger.

• It is a boss with three phases. Watch for the big warning signs before each attack.
• Giants are too big to knock back.
• It heals itself over time. Fire damage stops the healing.
• It helps the other baddies, so take it out first.

Old Mother Hollowbark in the campaign

On Normal you'll face one Old Mother Hollowbark 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 crooked, friendly-spooky old tree with a face in her bark (a big knothole mouth, bushy moss eyebrows), long twig fingers, a shawl of hanging moss, a pointy witch hat made of a curled leaf, and a swinging firefly lantern. Teal and plum palette. Gag: squirrels live in her hat; they peek out and throw acorns too, and they applaud when she's defeated.

The elite version

"Deep Roots": root spikes target two units at once, and the lantern needs four hits.

Similar enemies

• Big Bruno, Ogre Chief
• The Brass Colossus
• Mushroom Shaman
• Moss Troll

See every foe in the enemy almanac, or read the Day 12 walkthrough.