Tentacle Helmet or Helm of Tentacle is an item described in Monster Girl Encyclopedia World Guide - Side II.
Guide Book Entry
You have to be careful with the equipment you encounter in the castle grounds. You especially need to be careful with the item called "Tentacle Helmet". Such helmets are notorious for causing various malfunctions and even Dark Knights, who know how to handle magical equipment, cannot always cope with them. As the name implies, there is a tentacle brain plant inside such a helmet, so it is essentially a pot for these tentacles. You can see how, at the command of the tentacle brain, such a helmet jumps around the castle or moves on its own. Despite the ominous appearance of the object itself, the tentacle helmet innocently bouncing around the castle looks more charming than scary. It is very friendly to people and can even be petted. But contrary to this behavior, if you grab the helmet with your hands, you will be embraced by countless tentacles, which will slip out of it, led by a tentacle brain. When attacking a woman, the tentacle brain will instinctively try to put his helmet on her head. Absorbing the mana of the woman who happens to be wearing the helmet, the tentacles will sprout one by one and spread across her body, forming a semblance of armor around the woman who is caught. After she is wrapped in this armor of tentacles, she will continue to enjoy the pleasure of the tentacles inside the armor. She will also taste pleasure from the outside as she pounces on the man she loves, guided by the tentacles for a constant source of essence. Though her life will not be threatened, any girl with this helmet on her head will be exhausted to the point of unconsciousness by countless tentacles. By the time she wakes up again, it will appear that her body has changed: from the pleasure and mamono mana she has received, the girl will become a succubus.
In the past, when monsters led by Druella invaded and overthrew the religious authority of Lescatie, the tentacle brain possessed by one of the invading monsters found the helmet "on its own" and decided to put down roots in it. Nowadays, however, as mentioned above, such helmets catch not only human girls, but occasionally Dark Knights or monster couples who also enjoy the tentacles get caught in their tentacles. Definitely, this outfit stands out for its strangeness among other things and seems to be a danger to the mamono themselves.
The fact is that the current Lescatie is always rich in fresh magical power, which is generated through the efforts of a multitude of adoring monster couples. Such an atmosphere seems to be very comfortable for tentacle plants. Therefore, the tentacle plants that inhabit the inside of this helmet seem to be as ferocious as the species that inhabit the deepest part of the Tentacle Forest. I mean, from the outside it seems like an indescribably horrible piece of equipment, yet some Dark Knights dare to wear it to appease their bodies. Also, some monster couples voluntarily use this helmet together to engage in extreme tentacle debauchery...
...This thing makes me immorally uneasy about whether I should use it a little for my further training.
