Wondrous item, artifact (requires attunement)
This tight-fitting brass helmet feels very light, even lighter than expected of its thin-walled construction and small size. Dozens of smooth tentacles adorn the entire exterior surface. A combination of tarnish and black lacquer gives the tentacles a sense of motion with subtly varying shades of dark greys and blacks. When worn and attuned, the tentacles actually ripple and flow, snugging the helmet closer to the wearer's head and making it nearly impossible to remove without a remove curse spell. It radiates strong Illusion and Enchantment magic, with a dash of Divination and Transmutation.
Created by an elder brain named Zahdu'un and its powerful colony of mind flayers, the Dread Helm wanders the planes looking for strong minds to bond with and eventually recruit into the colony. The helm's powers center around fear and nightmares, causing psychic damage and exhaustion from great distances against a single target. It subtly works against the wearer as well, breaking down mental resistance and molding the mind into something more suitable to join Zahdu'un's colony.
When worn, the Dread Helm lets the wearer know the location of any thinking being within 60 feet. The helm automatically blocks telepathy, detect thoughts, and any other form of mental probe or messaging (message, sending, etc.), and it will cause 3d6 psychic damage in mental feedback to the effect's caster (Wisdom saving throw DC 16 to negate) unless the wearer allows the mental connection to go through.
The wearer can bind a target to the Dread Helm by sympathetic magic - taking a few of the target's hairs or fingernails (or other body parts) and using gum arabic to stick them to the helm during the course of a 10 minute ritual. The wearer can use the helm's powers to affect the bound target regardless of range as long as they occupy the same plane of existence.
The Dread Helm has 30 charges and regains 4d6+4 charges every day in the darkest moment of the night. The wearer may use an action to expend one or more charges to cast one of the following spells from it, using your spell save DC (or 12 plus Intelligence bonus if not a spellcaster): detect thoughts (1 charge), dream (5 charges), fear (3 charges), phantasmal killer (4 charges), suggestion (2 charges), weird (9 charges). Each of these spells can target the helm's bound target regardless of range as long as the wearer is on the same plane of existence. Against the helm's bound target, each spell can be cast once per day without using charges.
When the wearer uses the helm's powers or causes pain to others, the Dread Helm directly stimulates the brain's pleasure centers, eventually leading the wearer into full-blown case of sadism after a few days or weeks of using the helm's powers. The wearer can resist this effect every day they use the helm's powers with a Wisdom saving throw DC 15. The DC increases by +1 per previous saving throw attempt.
Zahdu'un maintains a psychic link with the wearer of the Dread Helm, though initially the wearer believes they sense the helm tickling the back of their mind and not the helm's creator. Zahdu'un can talk with the wearer, and it can plague the wearer with nightmares, suggestion spells, and invasive thoughts in an attempt to exert control over the wearer's actions and beliefs. Eventually influencing the wearer to travel to the astral plane and go through the transformation to become a mind flayer and join the colony.
Zahdu'un can break attunement to the helm and force it to fall off the wearer's head, if it believes the wearer doesn't have the required intelligence to join the colony. Encasing the Dread Helm with an inch or more of lead on all sides will temporarily break the psychic connection.
Rumors of damaging nightmares assumedly caused by the Dread Helm currently circulate around the Dwarven Kingdom. Once recovered by Krannock Steelshanks, the Dread Helm will stay in a locked box lined with 2 inches of lead on all sides in the Forgotten Flat.