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The Brain of Mensis is a Great One in Bloodborne.


The Brain of Mensis is a massive brain-looking creature, covered in eyes, with a long twisted arm that ends in a beastly clawed hand.

It is the reason why the Hunter is afflicted with Frenzy when first arriving in the Nightmare of Mensis. A lever can be activated, triggering a cutscene in which the Brain is dropped into the abyss of the tower it overlooks. After this is done, the Hunter will not receive damage when walking outside the tower.

Once the Brain has been dropped, the Hunter can finish it off by accessing a dark abyss via a newly-available cage elevator in the Panopticon. Broken and helpless, the Brain is incapable of attacking the Hunter in any way, observing them and following it with its now harmless and pitiful gaze.



Upon investigating the Nightmare, the School of Mensis discovered an eldritch mind, lined with the sacred and elusive "eyes on the inside" that were said to be the key to evolution. But these eyes were of some inexplicably evil nature, and the brain had immense rot, so that its gaze would drive mortals lethally mad with Frenzy even though they could not see it from a large distance. Despite this, the Brain of Mensis was still a true Great One, and the scholars left it there.


  • The Brain of Mensis drops a Living String when slain. After acquiring said item, it will be available for purchase in the Hunter's Dream, from the Insight Bath Messenger. However, players should "make contact" with it first.
  • The Brain of Mensis will respawn after being killed, but only drops the Living String once.
  • A Moon Caryll Rune can be obtained by using the "Make Contact" gesture near the Brain of Mensis. A known spot to stand is at its middle finger and facing its right eye. Note that it will take a full minute before getting the rune.
    • This rune states that Great Ones living in the Nightmare are helpful in nature, possibly explaining why this one gives you items when the gesture is used, though that seems odd considering that it has fallen into a pit by your hand.
      • Since the Moon Caryll Rune increases the amount of Blood Echoes obtained after killing the enemies, it's possible for the brain to be actually indirectly asking the player to euthanize it and put it out of its misery.
  • After acquiring the Moon Rune, the "Make Contact" gesture will produce a Great One's Wisdom, although this only works once.
    • The gesture can also be used after the creature has been slain.


  • The Brain of Mensis is the only Great One that isn't considered a boss. In fact, it actually respawns.
    • Oddly enough, the Brain of Mensis appears to have a very large health pool. About 8500 HP to be exact, almost like an actual boss.
    • The Brain of Mensis only cries out in pain when it is finally killed, although it is completely helpless against the player.
  • Mensis means "month" in Latin and is the term used to refer to the period in a woman's menstrual cycle where there is discharge from the womb lining commonly referred to as a period. It occurs once in a lunar cycle of approximately 28 days and the naming could be important considering the game's central themes of birth and effects of the moon.
  • According to the description on Living String the Brain of Mensis is terribly rotten. Not only that, but it appears that the Brain was somehow retrieved from the Nightmare itself, yet it would seem that it was in fact created in said Nightmare as it seems impossible that one could extract such a dangerous being from the Nightmare.
  • There is a theory that the Brain of Mensis was born from the collective minds of the School of Mensis when they projected themselves into the Nightmare realm. This somewhat makes sense besides the obvious point of its physical appearance resembling an actual brain, as the Brain of Mensis has an interesting detail. It has two arms, and on each hand, there are six fingers. These amounts of fingers are associated with the Kin, which are humans who transcend humanity. Perhaps the sacrifice of the entire school created something that was truly devoid of humanity, and the fingers are but a memory of its origin.




Bloodborne - Brain of Mensis Location (and Blood Rock Location)