Board Thread:Versus Battles/@comment-31165326-20181113050408/@comment-28876888-20181114040526

https://jambrose.info/file_browser/Dungeons%20and%20Dragons/DnD%205e/Rulebooks/Supplements/Volo%27s%20Guide%20to%20Monsters.pdf

Page 174. The Elder Brain is the hive mind of all Mind Flayers of its colony, and upon death absorbs their mind.