Alienation

Alienation represents a character's growing knowledge and the resulting insanity that comes with confronting eldritch truths.
A character without an Alienation score is considered Ignorant; they are generally sane and have never encountered something from the Far Realm. By contrast, a character with a high Alienation has deep insight into the universe, but borders on being insane, for a mortal mind cracks and warps under such weight. A character with the maximum Alienation score of 20 has embraced some part of true understanding, which drives them utterly and irrevocably mad.

Alienation Score

Progressively higher Alienation scores are divided into the following levels, each of which grant a unique feature while your Alienation score is in that range.

Ignorant

You know nothing of the terrors of the world. Sleep soundly, child, for there is nothing that can harm you.

Aware (1-4)

You have experienced the unthinkable, learned a scrap of forbidden knowledge, or seen something from beyond the mortal world. Your eyes have been opened to the fathomless terrors of the universe and they can never be closed. Once you gain your first point of Alienation, you can't lose it.
Unsettled. You have disadvantage on saving throws against being charmed or frightened.

Paranoia (5-9)

You have supped of forbidden knowledge and crave even more, yet constantly you find yourself looking over your shoulder, terrified of the consequences of what you have learned. Wherever you look, new patterns take shape, and with few exceptions, they spell danger for yourself and the world at large.
Conspiracy. When you roll a critical hit or a critical failure on an attack roll, roll any die. On an odd roll, a critical hit becomes a critical failure, and vice versa.

Dread (10-14)

You can feel the weight in your gut with every moment of apprehension. Horrors do not simply await you in far-flung realms, but around every corner, and inside every cupboard, waiting to rend you asunder for your trespasses. Worse still, you now know that the greater conclusion is inevitable: when the stars are right, the Old Ones shall return, and everything shall come to a monstrous end.
Defenseless. Your armor class decreases by 2.

Mania (15-19)

The strain on your mind has formed cracks, which show evidently on your thinking and behaviors. By degrees, the normal patterns of the world have grown foreign, replaced with alien designs and esoteric forms.
Frenzy. Whenever you deal damage with a melee attack, you can add your Intelligence, Wisdom, or Charisma modifier to the damage roll. However, your maximum hit points are decreased by your level.

Revelation (20)

Your mind reels as the totality of perspective comes crashing in like a wave. You have achieved a revelation, a fragment of the Old Ones' wisdom from beyond the stars. Whatever hope you once held of maintaining your sanity is lost. Everything you previously knew was but shadow puppets on a cave wall, and now, stepping into the cold, bright light of understanding, you can see vistas more terrifying than man was meant to know. Once you gain 20 points of Alienation, you can’t lose them. Nothing short of a wish spell can repair your damaged psyche.
Insanity. When you finish a long rest, roll twice on the Long-Term Madness table, you are afflicted by those madness until you next finish a long rest.

Losing Alienation

Too much Alienation has disastrous effects on a mortal mind. A character can lose a point of Alienation by spending a long rest restlessly asleep, pitching and turning with fitful dreams. The character does not regain hit points or hit dice over this long rest nor does it regain expended spell slots of 4th level or higher.
A character may attempt a cleansing ritual, but they risk their soul in the process.

Alienation Checks

You might call for an Alienation check when a character seeks to understand or interact with the creatures or items that have been touched by the Far Realm.

Alienation Saving Throws

You can call for an Alienation saving throw at any time a character is confronted by the fathomless wisdom of the Great Old Ones or the surreal inhabitants of the Far Realm. Some creatures might also call for an Alienation saving throw to resist the mind-altering effects of madness.

Statistics based on the Lovecraft Handbook by Mage Hand Press