Madness Domain (Cleric Divine Domain)

(This divine domain uses spells from Xanathar's Guide to Everything.)

A glimpse into a desolate future, an exposure to the insanity of the multiverse, the numbing uncertainty of dire circumstances, among many other occurrences, all lead to a decline into madness. Instead of imprisoning themselves in their insanity, followers of madness not only dwell in it, but are empowered by it, embracing it as a twisted extension of their mortal knowledge. Followers seek to cause turmoil wherever they go, causing even the stoutest to fall into fits of lunacy. These clerics are so dedicated to bringing madness to others that they willingly enter the realm of insanity themselves.

The gods of this domain are fickle, but also as equally insane as their devotees, becoming incessant with even minor quests, believing in foolish prophecies, and spreading chaos in their pursuit of forbidden knowledge and power. Some of these deities include Azathoth, Cthulhu, Cyric, Dionysus, Ghaunadaur, Lyssa, Nyarlathotep, Tharizdun, and Urundishen, among other mad gods or those that seek to spread insanity.

Madness Domain Spells
At each indicated cleric level, you add the listed spells to your spells prepared.

Broken Mind
Starting at 1st level, roll or select a form of indefinite madness, as listed in the Indefinite Madness Table (DMG, pg. 260). This madness cannot be cured except by a wish spell. With your mind full of turmoil, you are immune to being charmed, and you have advantage on saving throws against being frightened.

Whispers from the Void
Also starting at 1st level, your words are laced with whispers from the void, rendering your spells more effective. Whenever a spell you cast would deal damage to a creature, the spell deals an additional amount of psychic damage equal to 2 + the spell's level. You also gain the vicious mockery cantrip, which counts as a cleric cantrip for you.

Channel Divinity: Incite Madness
Starting at 2nd level, you can use your Channel Divinity to incite madness within a creature. As an action, you choose a target to make a Wisdom saving throw. On a success, the target takes 2d6 psychic damage and is randomly afflicted with a short-term madness determined by the Short-Term Madness Table (DMG, pg. 259). This madness lasts for one minute or until the creature takes damage.

On a failed save, the creature takes 4d6 psychic damage and is randomly afflicted with a long-term madness determined by the Long-Term Madness Table (DMG pg. 260). In addition, the target's AC is reduced by 2, this reduction increases to 3 at 9th level, 4 at 13th level, and 5 at 17th level. This madness lasts for 1 hour, and whenever the creature takes damage, they can make another Wisdom saving throw, ending the madness on a successful save.

Might of Insanity
Starting at 6th level, your increasing madness grants an increasing power. You have an Insanity modifier which is equal to half your cleric level, round up. Your Insanity modifier is added to your Spell Save DC and your Spell Attack modifier.

This increase in power comes at a cost. Wisdom skill checks and saving throws you make are reduced by your Insanity modifier. Sometimes, however, your madness can be broken by a brief catharsis and a moment of clarity. Before you make a Wisdom skill check or saving throw, you can choose to ignore the reduction and instead gain a bonus to the roll equal to your Insanity modifier. You can use this trait a number of times equal to your Wisdom modifier (minimum of once), and you regain expended uses when you finish a long rest.

Maddened Spellcasting
Starting at 8th level, you add your Wisdom modifier and your Insanity modifier to the damage you deal with any cleric cantrip.

Void's Eye
Starting at 17th level, your mind has become a void of forbidden knowledge, shattering your psyche and rendering it impossible to navigate for others. You have resistance to psychic damage.

Your thoughts can't be read by telepathy or other means unless you allow it. If you allow a creature to read your thoughts or communicate with you telepathically, they gaze into the void within, their own mind becoming surrounded by the maddening screams. The creature must make a Wisdom saving throw, taking 6d6 psychic damage on a failed save, and half as much on a successful save, you then take an amount of psychic damage equal to half the damage dealt.

Additionally, you may spend 1 minute to call upon forbidden knowledge from the void, and you gain an effect as though you cast the legend lore spell. If you do so, you take 8d6 psychic damage. You can use this feature a number of times equal to your Insanity modifier, and you regain expended uses when you finish a long rest.