[Infernal] Weapon - Squirm

I like the idea that this weapon might try to kill you (and has the means to do so) if you don't listen to it. The balance for the weapon seems fine in the final inspection - it should be hard to get the maximum extra attacks out of this weapon unless you're really multiclassing (it should be rewarding if you're an Eldritch Knight); and even if you are, you'd have to be fighting a lot of enemies within the radius (so not necessarily the most useful if it's a boss or big bad).

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Long spectral lashes sprout from the handle of this whip, each wriggling in the air like excavated worms and moving as if it has a mind of its own. The lashes represent not only the mind of the entity within, but the merged mind of the wielder as well.

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Squirm
Weapon (whip), legendary (requires attunement)

To attune to this magic whip, you must hold its handle against your head for the duration of the attunement period and allow its spectral lashes to bind with your mind. The process renders you frightened and incapacitated for the duration as the spectral lashes wriggle across your body. At the end of the attunement period, the whip gains access your memories.

Sentience. Squirm is a sentient neutral evil weapon with an Intelligence of 18, a Wisdom of 13, and a Charisma of 16. It has hearing and darkvision out to a range of 120 feet. The whip can read, speak, and understand Common, Abyssal, and Infernal; it can communicate telepathically with its wielder or any creature the whip has hit within the past minute. It also has a walking speed of 1 feet.

A sadistic agon named Etzerai lives inside this whip or is the whip itself — it is unclear since the whip appears to be alive. It relishes in the mental torture of innocents, instilling fear, despair, and anguish whenever it can. If you have not fulfilled its thirst for some time, it either tortures you with your guilty memories or attempts to strangle you in the night.

Joined Mind. While you hold the whip, you have the following benefits: 

• You can telepathically communicate with creatures you see within 120 feet of you. 
• You gain darkvision out to 120 feet if you don't already have it. 
• You have advantage on Intelligence saving throws.

Arms of Deliria. You have a +2 bonus to attack and damage rolls made with the whip and you deal an extra 2d4 psychic damage when you hit with it. When you roll a 20 on the d20 for an attack roll made with the whip, the target is frightened of you until the end of its next turn. While frightened this way, a target cannot take reactions.

Psychic Thrash. The whip has a number of lashes equal to 1 + your Intelligence modifier (minimum of 2). On your turn as an action, you can make one melee weapon attack with each lash against a different target within reach.

Mind Strike. While holding the whip, you can use an action to cast confusion from it (spell save DC 17) without providing material components. Once used, this property can't be used again until the next dawn.