Shapechanger. The brain hood can use its action to polymorph into a Tiny or Small animal for which it has used Merge with Beast (or a Tiny or Small version of a larger animal) or back into its true form. Its statistics, other than its size, are the same in each form. While polymorphed into a beast, it can’t use Merge with Beast, but it can use Speak with Beasts as if it had merged with the polymorphed beast. The brain hood reverts to its true form if it dies.

The brain hood loses its 1/day Innate Spellcasting. It gains the shapechanger tag.

Green Hood

Some brain hoods have adapted themselves to further antagonize druids. These green hoods, which have an oily green coloration and spiky roots in place of its tentacles, use plant creatures as hosts.

Merge with Plant. If the green hood successfully hits a plant with an Intelligence of 5 or lower with its Slam attack, it latches onto the plant’s head or crown and attempts to control the creature. The target must succeed on a DC 14 Intelligence saving throw or become bonded with the green hood, losing all control of its body to the green hood. While bonded in this way, the green hood’s statistics are replaced by the statistics of the plant, including the plant’s hit points and Hit Dice, but the green hood retains its alignment, personality, Intelligence, Wisdom, and Charisma scores, along with its Speak with Plants trait. In addition, the green hood retains its ability to cast spells. If merged with a plant of Intelligence 4 or higher, the green hood loses access to its 3/day Innate Spellcasting for the duration plus 1 round after. If merged with a plant of Intelligence 6 or higher, it loses access to its 1/day Innate Spellcasting for the duration plus 1 round after. The green hood can’t be targeted specifically while bonded with a creature. It can detach itself from the creature and end the bond by spending 5 feet of its movement. If the bonded creature is reduced to 0 hit points, the green hood is ejected from it and appears in an unoccupied space within 5 feet of the creature.

Speak with Plants. While merged with a plant, the green hood can communicate with plants of the same type as if they shared a language.

Innate Spellcasting (Psionics). The green hood’s spellcasting ability is Intelligence (spell save DC 13, +5 to hit with spell attacks). The green hood can innately cast the following spells, requiring no components.

• At will: poison spray, produce flame, shillelagh, thorn whip
• 3/day each: detect magic, entangle, faerie fire
• 1/day each: call lightning, hold person, thunderwave

New Magic Items and Spells

The following magic item and spell are inspired by abilities possessed by a brain hood.

Disk of Beast Command

Wondrous item, very rare (requires attunement)

This flat black disk crafted from a brain hood corpse is oily to the touch. If you hit a beast with an Intelligence 3 or less with a melee or ranged attack with the disk, the beast must succeed on a DC 14 Intelligence saving throw or become bonded with you. While bonded with you, the beast is charmed by you until you use an action to remove the disk. While you are bonded with the beast, you have a telepathic link with it as long as the two of you are on the same plane of existence. You can use this link to issue commands to the creature as a bonus action. You can use your action to take complete control of the beast until the end of your next turn. The disk cannot be used this way again until the next dawn.

Curse. Ten percent of these disks are cursed, and the brain hood is only dormant rather than dead. Becoming attuned to it creates a low-level bond between you and the brain hood. As long as you remain bonded, you are unwilling to part with the disk, keeping it within reach at all times. Whenever you see an applicable beast, you must succeed on a DC 14 Intelligence saving throw or place the hood atop your head. The brain hood merges with and gains control of you. At the end of each of your turns, you can make another Intelligence saving throw. On a success, you can remove the disk.

Rubbery Body

2nd-level transmutation (sorcerer, wizard)
Casting Time: 1 action
Range: Touch
Components: V, S, M (a brain hood tentacle)
Duration: Concentration, up to 1 minute

This spell changes the flesh’s composition of a willing creature you touch to an oily rubber. Until the spell ends, the target has resistance to bludgeoning damage.

At Higher Levels. When you cast this spell with a 5th-level spell slot, the duration is concentration, up to 1 hour. When you cast this spell with a 7th-level spell slot, the target has immunity to bludgeoning damage until the spell ends.

Brain Hood Adventure Hooks

• A brain hood has focused its malicious attention on a local farmer. Once a week, a cow or horse belonging to the farmer rampages through the nearby village, injuring people and causing some property damage. Anger toward the farmer escalates when one of the horses kicks a villager hard enough to kill him.
• A wizard has experimented on a brain hood, enabling the creature to control humanoids. While his first tests with the creature have been successful, he becomes frustrated by the limitations on the level of intelligence the brain hood can control. He arranges the kidnapping of several people to continue his experiments to improve the brain hood’s capabilities.

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The Tome Unbound series fleshes out monsters from the Tome of Beasts 2, giving GMs ways to modify the existing monsters to surprise well-prepared players or to introduce monsters to a campaign.