Masked Mannequin

This quest can only be completed after you have built the twins swingset.

Head to the Normal version of the map, and inside the Green House Upstairs under the lamp, you'll find a masked mannequin head that you can interact with to pick up.

Once interacted, the head will float toward a headless mannequin in the Green House Backyard and spawn a bunch of purple-eyed zombies that you'll need to kill to feed the mannequin head with souls.

Once completed, you'll then need to escort the head to two more headless mannequins where you'll have to feed it with souls again, and after you've fed the final mannequin, the head will attach to the mannequin and begin spinning around before exploding with all your rewards.

These rewards scale with the round you're on. Past Round 25, you'll get Flawless Aetherium Crystals, Legendary Aether Tools, and potential wonder weapons.