This is a reinterpretation of the 3.5e Alienist prestige class. I have tried to stay fairly close to the original, adapting core features of the 3.5e class to 5th edition while trying to keep its ‘going more and more insane as you grow more powerful’ flavor.

Alienists deal with powers and entities from terrifyingly remote reaches of space and time. For them, magical power is the triumph of the mind over the rude boundaries of dimension, distance and often sanity. With knowledge and determination, they pierce the barrier at the edge of time itself. In the Far Realm, outside of time, Herculean minds drift, absorbed in contemplations of madness. Unspeakable beings whisper terrifying secrets to those who dare communication. These secrets were not meant for mortals, but the Alienist plunges into abysses of chaos and entropy that would blast a weaker mind. And slowly becomes mad as a result.

Alienist Features

Sorcerer Level	Feature
1st	Alienist Spells, Alien Intervention
6th	Distorted Shape, Alien Guidance, Rend Resistances, Secrets of the Far Realms
14th	Erratic Growth, Nullifier, Secrets of the Far Realms
18th	Secrets of the Far Realms, Transcendence

Alienist Spells

1st-level Alienist feature

You learn additional spells when you reach certain levels in this class, as shown on the Alienist Spells table. Each of these spells counts as a sorcerer spell for you, but it doesn’t count against the number of sorcerer spells you know.

Whenever you gain a sorcerer level, you can replace one spell you gained from this feature with another spell of the same level. The new spell must be a conjuration, divination or enchantment spell from the sorcerer, warlock, or wizard spell list.

Alienist Spells

Sorcerer Level	Spells
1st	Mind Sliver, Arms of Hadar, Expeditious Retreat
3rd	Misty Step, Tasha’s Mind Whip
5th	Fear, Intellect Fortress
7th	Evard's Black Tentacles, Summon Aberration
9th	Contact Other Plane, Far Step

Alien Intervention

1st-level Alienist feature

An alien from the Far Realms shows a distant interest in you. As a bonus action you can spend 1 sorcery point whenever you make an attack roll or a saving throw, roll a d4 and add the number rolled to the attack roll or saving throw.

Distorted Shape

6th-level Alienist feature

At 6th level, alien whispers warn you of incoming attacks. As a reaction, you can spend 2 sorcery points to cast the Blur spell without expending a spell slot.

Once you use this feature, you can’t do so again until you finish a short or a long rest.

Secrets of the Far Realm

6th-level Alienist feature

As you continue to listen to the mad whispers from the Far Realms, you learn their secrets, but it comes at a high cost: your sanity.

Starting at level 6, you permanently lose 2 points of Wisdom, but in exchange you learn two of the following secrets.

You lose 2 extra points of Wisdom in exchange for two additional secrets at 14th level.

Aberrant Companion

You are granted the service of a companion from the Far Realm, a spirit that takes the form of an aberration you choose: Gibbering Mouther, Intellect Devourer or Nothic. You learn the Find Familiar spell. The familiar has all the statistics of the chosen form, but it acts according to the rules of the spell.

Ability Score Improvement

You can increase one ability score of your choice - except Wisdom - by 2, or you can increase two ability scores of your choice by 1. As normal, you can’t increase an ability score above 20 using this feature.

Alien Resistance

You are granted a new and alien understanding of the matter and energy of the Material Plane. You either gain immunity to one damage type or resistance to two damage types of your choice: acid, cold, fire, lightning, poison, thunder.

Alien Restoration

Once per long rest, use your bonus action to regain half of your spent sorcery points, rounded down.

Insane Concentration

You can add your Charisma modifier (minimum 1) to Constitution saving throws that you make to maintain your concentration on a spell when you take damage.

Once you use this feature, you can’t do so again until you finish a short or long rest.

Magic of Madness

You learn two additional spells from the sorcerer, warlock or wizard spell lists. The spells must be of a level you can cast, and can never be higher than 5th level. The spells count as sorcerer spells for you, but they don’t count against the number of sorcerer spells you know.

Momentary Clarity

You force your mind into a state of extreme clarity, reducing the effect of your increasing insanity for a short period of time. As a bonus action you can spend 2 sorcery points to gain a +10 bonus on Wisdom saving throws. This bonus only applies when you have negative Wisdom ability modifier.

This effect ends after 1 minute or when you are incapacitated.

You can use this feature multiple times, but you pay a heavy price for forcing your mind to have these brief moments of insight. Every time you use this feature, you gain a level of exhaustion after the effect wears off.

Relic of the Far Realm

A magic item of unknowable power is bestowed upon you. As the fabric of time and space rips open a strange crystal shard falls at your feet. You may add a Far Realm Shard to your inventory.

Alien Guidance

6th-level Alienist feature

You can call upon the aliens of the Far Realm to help you in battle, trying to turn failure into success. When you make an attack roll or saving throw that fails, you can spend sorcery points according to the Alien Guidance table to roll an extra die and add the result to the failed roll. You choose the die size before or after the attack roll or saving throw, but without knowing by how much you failed.

Once you use this feature, you can’t do so again until you finish a long rest, unless you spend 5 sorcery points to use it again.

Alien Guidance

Die Size	Sorcery Point Cost
d6	3
d8	5
d10	6
d12	10

Rend Resistances

Starting at level 6 you can concentrate to radiate an aura of malign alien presence that reduces the resistances of your enemies. The radius of the aura is 20 feet in all directions and functions as a concentration spell. As a bonus action, choose a damage type: acid, cold, fire, lightning, poison, thunder. Damage of the chosen type is doubled for all enemies within the aura for 1 minute or until your concentration is broken. That means that enemies that have damage resistance, and would otherwise take half damage, take normal damage instead and enemies that have a vulnerability to the chosen damage type take four times damage. Enemies that are immune to the chosen damage type are not affected.

Once you use this feature, you can’t do so again until you finish a long rest.

Erratic Growth

14th-level Alienist feature

Your continuous interaction with beings from the Far Realm not only affects your mind, but starts to change your body as well. You undergo a minor physical change, like growing a small tentacle or other strange feature, such as an extra appendage, organ, eye, or enigmatic lump. You can hide this abnormality in a robe or hood, but the alien growth is not under your control and sometimes moves, twitches, opens, or otherwise animates of its own accord.

Secrets of the Far Realm

14th-level Alienist feature

As you continue to listen to the mad whispers from the Far Realm, you learn their secrets, but it comes at a high cost: your sanity.

You lose an extra 2 points of Wisdom in exchange for two additional Far Realm secrets.

Nullifier

14th-level Alienist feature

At 14th level, the radius of your aura granted by the Rend Resistances feature increases to 50 feet and lets spells and attacks circumvent enemies’ damage immunities. Enemies that are immune to the chosen damage type are now considered resistant to that damage type and so take half damage.

Transcendence

18th-level Alienist feature

By transcending the mortal plane, you lose your mind entirely to the Far Realm. The knowledge accrued in your adventures is driving you mad beyond relief, but the power you have gained is matched by few.

You lose an additional 2 points of Wisdom, but you gain all of the following features:

• You can create spell slots beyond 5th level. As a bonus action, you can spend a number of sorcery points to create a spell slot of 6th level or higher, according to the Creating Spell Slots Above 5th Level table below.
• As your mind is almost entirely gone and there is not much left to damage anymore, you become immune to psychic damage.
• Anyone trying to cast a mind affecting spell on you must make a Wisdom saving throw, DC 18. On a failed save you lash out with alien energy, causing the spell to fail. Additionally, the caster takes 2d8 psychic damage and has disadvantage on the next attack roll or saving throw. On a successful save, all spell effects of the cast spell (damage and/or duration) are halved.

Creating Spell Slots Above 5th Level

Spell Slot Level	Sorcery Point Cost
6th	9
7th	11
8th	12
9th	14