Monster. Brute.
During activation, each Tentacle can declare an attack and add to the attack

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At the end of activation, Swamp Thing can remove any number of tentacles from the Battlefield or place any number of Tentacles in adjacent hexes with Head.
All parts of the model are considered a single creature.
Game effects cannot cause the Swamp Thing to move or be replaced, except for its own movement. Only Head moves during activation.
If Tentacle takes damage, the Swamp Thing takes 1 damage and that Tentacle is removed from the Battlefield.
Tentacles can still be at any distance from the Head if they were placed and not removed after movement.