Brachavyrm

Body Arms. The brachavyrm gains a pair of arms each time it consumes a humanoid creature. For every five pairs of humanoid arms the brachavyrm has, its speed is increased by 5 feet. A pair of arms wither and die after a month it was created.

Spider Climb. The brachavyrm can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Multiattack. The brachavyrm makes four attacks: one with its bite, one to constrict, and two with its tail stingers. It can replace its bite attack with swallow or web spray, if available.

Bite. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 10 (1d10 + 5) piercing damage and the target is grappled (escape DC 15). Until this grapple ends, the target is restrained, and the brachavyrm can't bite another target.

Constrict. Melee Weapon Attack: +9 to hit, reach 5 ft., one Huge or smaller creature. Hit: 16 (2d10 + 5) bludgeoning damage plus 16 (2d10 + 5) slashing damage. The target is grappled (escape DC 19) if the brachavyrm isn't already constricting a creature, and the target is restrained until this grapple ends.

Tail Stingers. Melee Weapon Attack: +9 to hit, reach 10 ft., one creature. Hit: 10 (1d10 + 5) piercing damage and the target must succeed on a DC 16 Constitution saving throw or become poisoned.

Swallow. The brachavyrm makes one bite attack against a Medium or smaller target it is grappling. If the attack hits, the target is swallowed, and the grapple ends. A swallowed creature is blinded and restrained, it has total cover against attacks and other effects outside the brachavyrm, and it takes 11 (2d10) acid damage at the start of each of the brachavyrm's turns.

 If the brachavyrm takes 20 damage or more on a single turn from a creature inside it, the brachavyrm must succeed on a DC 14 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the brachavyrm. If the brachavyrm dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 5 feet of movement, exiting prone.

 If a swallowed creature dies and the creature is a humanoid, the corpse's body is consumed and a pair of arms sprout from the brachavyrm's body. When this happens, the creature can only be restored to life only by means of a resurrection spell or greater.

Web Spray (Recharge 5-6). The brachavyrm spits webbing in a line that is 30 feet long and 10 feet wide. Each creature in that line must succeed on a DC 16 Dexterity saving throw or be restrained by webbing. As an action, the restrained creature can make a DC 15 Strength check, escaping from the webbing on a success. The effect ends if the webbing is destroyed. The webbing has AC 10, 5 hit points, vulnerability to fire damage and and immunity tobludgeoning, poison, and psychic damage.