Ruthless swings. For every 10 health that the longarms loses, it gains a 15% damage bonus

Fire aversion. Any fire damage dealt to the longarms removes its ability to transmit the plague.

Adapt. After the same type of damage is dealt to the longarms 2 times, it gains resistance to that type of damage. After that damage is dealt 2 more times, it gains immunity.

Multiattack. The longarms makes 2 arm swing attacks or 1 bite attack.

Tentacle swing. Melee Weapon Attack: +11 to hit, reach 20 ft., X targets. Hit: 14 (2d10 + 6) slashing damage damage. All creatures in a 25 foot cube are affected by this attack. The targets have to make a DC 12 constitution saving throw or become infected by the plague.

Toothy bite. Melee Weapon Attack: +12 to hit, reach 10 ft., 1 target. Hit: 19 (3d12 + 2) piercing damage.