Elder brain

An Elderbrain is a collective of minds of past illithid that resides in an Illithid hive. It psychically connects all illithid to each other and provides knowledge of past events, anything that an individual illithid sees, and is considered sacred by the species.

K'Varn gained control of an entire city of illithid by erecting a crystal-like structure above the Elderbrain which subverted its will. Later, Vox Machina nearly destroyed the Elderbrain in an attempt to escape from the mind flayers within the city.