Path of Derangement

Otherworldly powers grasp and worm their way into your mind, but your body is too strong. It forges on, unrelenting. Whether it is dreams, ideals, love, or sheer, indomitable will you are barely held together, constantly fighting off this preternatural influence. And you know you must force this intruder to submit to you before you lose yourself and you are turned into an empty puppet for its own devices.

This subclass channels the power of an unknown and potentially alien entity as it invades and alters the mind of a mighty warrior. Are you a soldier escaping from an Illithid colony? A sailor who has woken up in a strange den on an unknown island? Or even an explorer who was altered by the fringes of the multiverse? Whatever the origin, will you succumb to this invasion of your mind and body, or will you overcome this influence and use its powers to your own end? 

Synaptic Scream

 

At 3rd level your rage becomes unreliable as the entity within you attempts to exert control. At times of extreme stress or danger the creature may try to control you, forcing you to make a DC 12 Wisdom saving throw. On a failed save you enter a rage and must immediately attack the nearest creature or object until the end of your turn. If creatures are equidistant from you roll a luck check to determine your target. If you have the multi-attack feature you may divide the attacks to every creature nearby if you so choose. 

You may also elect to fail this saving throw. Instead of fighting off the influence you may direct it at a creature or object within sight. You then use all movement and attacks to focus on that creature or object until the end of your turn, or until it is destroyed or dead. At 10th level you gain advantage on this save. 

Also at 3rd level whenever you strike a creature with a melee attack you deal an additional 1d4 psychic damage. This damage increases to 1d6 at level 7, 1d8 at level 11, and 1d10 at level 15.

Poisoned Mind

At 6th level your dismantled mind becomes a natural defense against mental invasion. Any creature that attempts to read your mind or attempt any kind of divination spell with you as the target takes psychic damage equal to your level in this class and you become aware of the attempt. 

Additionally, the parasite in your mind detests outside interference. You gain advantage on saves against being charmed or frightened and, if you fail your saving throw, you immediately enter a rage - forgoing the condition for one turn so long as you use all movement and attacks on the creature causing the effect. The condition then takes hold at the end of your turn, so long as nothing has disrupted it. 

Supernatural Exertion

At 10th level your brain and the parasite within no longer heed your bodies self-imposed limits. Once per turn when you take the melee attack action you may choose to roll an additional damage die based on your current weapon. You take necrotic damage equal to the roll as well as add the damage to the attack total as your muscles move and stretch beyond their normal limits, damaging themselves in the process.

Additionally when you make a strength or dexterity skill check or saving throw you may roll 1d6, adding it to the total and taking double the damage rolled on the die. This damage cannot be reduced in any way. 

 

Emergence

At 14th level you and your parasite are fully merged. Either it has consumed your personality and left you a husk fit for the hive mind or your sheer force of will has overwhelmed it and you now hold complete control. Regardless, whenever you drop to 0 hp or are killed outright but your body is not destroyed (i.e. the disintegrate spell) you may choose to burst from your body as a modified intellect devourer. You retain your alignment, personality and barbarian abilities described in this class but your Constitution becomes 14 (+2), you lose all access to magic items, and and you may not access any other class features while in this form. This form has your unarmored AC, speed, stats and half your total HP. You rely on blindsight up to 60 ft. but you have access to the Detect Sentience feature. While in this form you may make either 2 attacks (STR or DEX plus proficiency) dealing 2d6+STR/DEX slashing damage or make one attack and use Devour intellect. The save is an 8+proficiency+constitution INT saving throw, dealing 4D10 psychic damage. If this psychic damage would bring the target to 0 hp you may forgo dealing damage and inhabit their body, controlling them and using their statistics and abilities. You may also inhabit one recently slain humanoid that has an intact head, rising with 1 hp. After a long rest you rewrite their form, regaining all previous abilities from before being ejected as an intellect devourer.