Multiattack. Two Spore-Laced Claw attacks or one Mycelial Harpoon attack and one Spore-Laced Claw attack.

Mycelial Harpoon. Melee or Ranged Weapon Attack: +5 to hit 5 ft. or range 15/30' one target 10 (2d6+3) piercing damage and harpoon sticks in target if it is a Med or smaller creature. While harpoon is stuck target: 7 (2d6) piercing damage at start of each of its turns marcher can't make Mycelial Harpoon attacks vs. others and target and marcher can't move over 30' from each other. A creature including target can take its action to detach harpoon via DC 13 Str check. Or mycelial thread connecting marcher to harpoon can be attacked and destroyed (AC 12; hp 10; vulnerability to thunder; immunity to bludgeoning poison and psychic) dislodging harpoon into unoccupied space within 5 ft. of target and preventing marcher from using Recall Harpoon.

Spore-Laced Claw. Melee Weapon Attack: +5 to hit, 5 ft., one target, 5 (1d4+3) piercing damage + 9 (2d8) poison.

Slowing Spores (Recharge 5-6). Releases spores from its cap. Each creature within 20' of the mush marcher: 18 (4d8) poison and is poisoned (DC 13 Con half damage and isn't poisoned). While poisoned this way creature's speed is halved. A poisoned creature can re-save at end of each of its turns success ends effect on itself.