Myrnath is the High Elf host of Us. He is encountered aboard the Nautiloid in the Prologue, on an upper ledge by a collection of brain jars, mind sanctuaries and tentacle aquariums. His skull has been partially removed to expose a quivering brain. Investigating further will reveal his brain to be a newborn Intellect Devourer.
Myrnath cannot be saved or spoken to. If Us is freed or killed, it will kill Myrnath too. If the player attacks and kills Myrnath before freeing Us, it will kill both Myrnath and Us.