Encryptid

Event: Encryptid is an event quest in the Fallout 76 add-on Wild Appalachia.

Quick walkthrough
The event summons an imposter sheepsquatch (a modified assaultron) and a constantly respawning horde of various other robots to defeat. It requires the party to activate pylons nearby to remove the shields that make the imposter sheepsquatch invulnerable before killing it to complete the event.

Detailed walkthrough
The event starts when a player character uses the terminal at the Pylon ambush site. Starting the event requires an assaultron recall keycard to be in the player character's inventory, and can only be activated if the event has not occurred on the server for at least three hours. Starting the event spawns a three star legendary sheepsquatch and a horde of other robots to attack any player character in the area, including a variant of the eyebot that moves in swarms and explodes on death.

The sheepsquatch is invisible and invulnerable until the three pylons nearby are activated. Activating a pylon places a damaging effect on the person who activated it and notifies all participants which party member has activated which pylon if they have the event tracked. The sheepsquatch becomes visible and loses its invulnerability as long as all three pylons are all active. If any of the pylons become deactivated through the death of the party member who activated it, the sheepsquatch becomes invisible and invulnerable again.

The event ends once the sheepsquatch is killed. At that point, further robots will not spawn, but those who were already spawned will remain active and hostile to those in the area.