Illithid - Nerve Swimmers

Distraction: Any living creature that begins its turn within a swarm must succeed on a DC 12 constitution saving throw. On a faillure the creature is poisoned until the end of its next turn.

Discern Lies: A nerve swimmer swarm that inhabits a host has advantage on all insight checks against the host.

Hive Mind: Any nerve swimmer swarm with at least half of its hit points forms a hive mind and has advantage on all Intellect, Wisdom and Charisma saving throws. When a nerve swimmer swarm is reduced below half its hit points, it cannot burrow into flesh or inhabit a host.

Bite.. Melee Weapon Attack: +7 to hit, reach 0 ft., one creature in the swarm's space. Hit: 11 (2d6+5) piercing damage, or 8 (1d6+5) piercing damage if the swarm has half of its hit points or fewer. The creature must succeed on a DC 15 constitution saving throw. On a faillure, the swarm burrows into its flesh. A swam that succeeds on this attack is considered to inhabit its host; it can use its domination, nerve strike, wracking pain, and discern lies abilities, but not its distraction or bite attack. A swarm might leave its host as a free action. To remove a burrowing nerve swimmer swarm, a heal spell or greater restoration spell must be cast upon the host.

Nerve Strike (5 / Long): A nerve swimmer swarm that inhabits a host can stop the host from taking conscious action by absorbing its nerve impulses. The host must succeed on a DC 12 constitution saving throw. on a faillure, the creature is affected as if by a hold monster spell. The nerve swimmers control the victim's body directly instead of the mind; therefore this ability is not mind-affecting. The victim can attempt a saving throw at the end of its round to end the effects of the nerve strike.

Wracking Pain (3 / long): A nerve swimmer swarm that inhabits a host can cause its host to suffer wracking pain. The host must succeed on a DC 12 constitution saving throw. on a faillure, the creature Strength score is reduced by 1d4. The target dies if this reduces its Strength to 0. Otherwise, the reduction lasts until the target finishes a short or long rest. Then the creature must succeed on another DC 12 constitution saving throw. On a faillure, the creature constitution score is reduced by 1d4. The target dies if this reduces its Constitution to 0. Otherwise, the reduction lasts until the target finishes a short or long rest.

Domination (1 / long): A nerve swimmer swarm that inhabits a host can force the host to obey its commands. The host must succeed on a DC 12 Constitution saving throw. On a faillure the creature is affected as if by a dominate monster spell. This control lasts for only 6 minutes. The nerve swimmers control the victim's body directly instead of the mind; therefore this ability is not mind-affecting.