Celvethus, Scuttling Death

Frag Chitin. Each time the creature is struck by a melee weapon attack, the attacker must succeed on a Dexterity saving throw (DC 12) or suffer 1d4 piercing damage.

Broodworm Host. Celvethus plays unwilling host to an Arcanamite Broodworm and, as such, is immune to psychic and necrotic damage. Instead, any damage of these types is applied directly to the Broodworm itself.

Weak Points. A crab is weakest at the joints, and Celvethus is no exception. The hit point and armor class values of Celvethus represent the hit point and armor class value of its main body or shell. When saving against a damaging area of effect, such as the Fireball spell, Celvethus' main body rolls against it as normal, and if Celvethus succeeds on the saving throw their limbs take no damage, and only half the damage on a failed saving throw.The statistics of Celvethus' limbs are as follows:
- Front, Middle, and Rear Legs: 10 HP each, AC 18 each. 6 in total, 3 on each side. The loss of one leg causes a loss of 5 feet of movement, and deals its own hit point maximum as damage to the main body. The loss of half of its legs disables the use of its Scuttle legendary action and confers disadvantage on dexterity saving throws. The loss of all its legs causes Celvethus to lose all its movement speed and fall prone and prevents the use of the Leg Bash action.
- Left & Right Claws: 25 hit points each, armor class 20 each. The loss of one claw causes a loss of the Multiattack action and deals its own hit point maximum as damage to the main body. The loss of both claws prevents the use of the Claw action and disables the use of the Snatch legendary action.

Innate Spellcasting. Celvethus may innately cast some spells. Its spellcasting ability is Wisdom (spell save DC16, +7 to hit with spell attacks). Celvethus can innately cast the following spells:
At will: Poison Spray (5th level), Shocking Grasp (5th level), Mind Sliver (5th Level)
3/day: Expeditious Retreat, Shield, Thunderwave (2nd level, 3d8)
1/day: Enlarge/Reduce

Multiattack: The Giant Enemy Crab makes two strikes with its claws.

Claw: Melee Weapon Attack: +7 to hit, reach 10 ft., 1 target. Hit: 2d6 + 8 Piercing damage.

Leg Bash: Melee Weapon Attack: +7 to hit, reach 15 ft, 1 target. Hit: 1d8 + 6 Bludgeoning damage.

Dash. Celvethus may take the Dash action as a bonus action on each of its turns.

Regeneration (Recharge 6). Celvethus regains a number of hit points equal to 2d10+3, and begins to regenerate. On each turn following the activation of this ability, Celvethus may use another bonus action to regain another 10 hit points to its body and 5 hit points to each of its limbs. This effect is suppressed upon receiving either fire or cold damage.

Shield (3/day). Celvethus innately casts the Shield spell, gaining a +5 bonus to its AC until the start of its next turn.

Celvethus can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. Calvethus regains spent legendary actions at the start of its turn.

Scuttle (Costs 1 Action). Celvethus immediately moves 10 feet without triggering opportunity attacks.

Snatch (Costs 1 Action). Celvethus immediately initiates a grapple attempt with a nearby enemy within range of its claws. A creature grappled in this way is restrained and shares Celvethus's space, traveling with it as it moves.