Subclass Warlock Great Old One Patron

What Is the Great Old One Patron?

The Great Old One Patron is a debuff-focused Warlock subclass built around psychic damage and debilitation. Psychic Spells at Level 3 lets you convert your damage spells to Psychic and cast Enchantment and Illusion spells without speaking. Entropic Ward at Level 6 spends a Pact slot to impose Disadvantage on an incoming attack. Thought Shield at Level 10 gives Psychic resistance and reflects a point of it back, and Eldritch Hex lets you pick which ability score Hex cripples.

Class Features

Progression Overview

LEVEL	FEATURE
3	Great Old One Spells, Psychic Spells
6	Entropic Ward
10	Thought Shield, Eldritch Hex, Hex (always prepared)

Level 3 Features

Great Old One Spells

Your Patron grants an always-prepared spell list that doesn't count against your Pact Magic limit:

WARLOCK LEVEL	SPELLS ADDED
3	Dissonant Whispers, Hideous Laughter, Detect Thoughts, Phantasmal Force
5	Fear, Hunger of Hadar
7	Confusion, Death Ward
9	Telekinesis

Psychic Spells

GreatOldOne_3_PsychicSpells — a toggle, on by default and placed on your hotbar. It does two things.

Psychic damage conversion. While the toggle is on, Warlock spells that deal damage deal Psychic damage instead of their usual type. This applies to the spell's own damage, including damage that arrives later — ongoing ticks, zone damage from summoned effects, retaliation, and rider damage all convert alongside the initial hit.

CONVERTS	EXAMPLES
Cantrip damage	Eldritch Blast, Chill Touch, Toll the Dead, Thunderclap
Spell damage	Arms of Hadar, Witch Bolt, Blight, Enervation
Delayed and recurring damage	Hell's Lash ticks, Cloud of Daggers, Hunger of Hadar, Witch Bolt upkeep
Retaliation and riders	Armour of Agathys, Hex, Hellish Rebuke
The spell's portion of weapon cantrips	Booming Blade, Green-Flame Blade, Vengeful Blade, True Strike

Some damage is deliberately left alone:

• Weapon damage keeps the weapon's own type. With Booming Blade or Green-Flame Blade, the weapon swing stays Slashing or Piercing and only the spell's added damage becomes Psychic. True Strike is the exception — it already replaces the weapon's damage type with Radiant, so that converts too.
• Spells that already deal Psychic damage are unaffected, since there is nothing to convert: Mind Sliver, Dissonant Whispers, Tide of Darkness, Mind Spike, Phantasmal Force, Shadow Blade, Dream, Synaptic Static.
• Summoning spells keep their damage. Animate Dead, Summon Fey and Danse Macabre deal damage through the creature they summon, not through the spell.
• Telekinesis keeps its Bludgeoning damage, which comes from the thrown object's weight rather than from the spell.

Subtle casting. GreatOldOne_3_PsychicSpells_Subtle — a hidden passive that removes the Verbal component from your Enchantment and Illusion spells and lets you cast them without breaking Stealth.

Psychic resistance is common on the higher-level enemies you meet, so the conversion is not a free upgrade — it is a lever. Turn it on to line up with gear that keys off Psychic damage or Mental conditions, and turn it off against anything that shrugs Psychic off. Because it is a toggle rather than a per-cast choice, switching costs you nothing but a click.

Level 6 Features

Entropic Ward

A Reaction, available in a free version on its own charge and in versions that spend a Pact Magic slot of Level 3, 4, or 5:

• Trigger: A creature makes an attack roll against you
• Cost: Your Reaction + one Warlock Pact Magic slot (Level 3, 4, or 5)
• Effect: The attack is made with Disadvantage
• On Miss: You gain Advantage on your next attack roll against that creature

The effect is identical regardless of which slot level you spend, so use the lowest one available. Pact Magic slots are scarce, which makes this worth saving for attacks you genuinely cannot afford to take.

Level 10 Features

Thought Shield

A permanent passive: Psychic damage you take is halved, and the creature that dealt it takes damage back. It pairs naturally with Psychic Spells: you are the one subclass that can flood a fight with Psychic damage without worrying much about it coming back.

Eldritch Hex

GreatOldOne_10_EldritchHex — when you apply Hex, you choose one of six Eldritch Hex variants to inflict alongside it:

VARIANT	STATUS	EFFECT
Eldritch Hex: Strength	ELDRITCH_HEX_STRENGTH	Disadvantage on Strength checks and Strength saves
Eldritch Hex: Dexterity	ELDRITCH_HEX_DEXTERITY	Disadvantage on Dexterity checks and Dexterity saves
Eldritch Hex: Constitution	ELDRITCH_HEX_CONSTITUTION	Disadvantage on Constitution checks and Constitution saves
Eldritch Hex: Intelligence	ELDRITCH_HEX_INTELLIGENCE	Disadvantage on Intelligence checks and Intelligence saves
Eldritch Hex: Wisdom	ELDRITCH_HEX_WISDOM	Disadvantage on Wisdom checks and Wisdom saves
Eldritch Hex: Charisma	ELDRITCH_HEX_CHARISMA	Disadvantage on Charisma checks and Charisma saves

Every variant covers both ability checks and saving throws for that stat. Constitution is usually the pick against casters, since it puts Disadvantage on their Concentration saves; Wisdom makes your Charm and Fear effects stick; Strength shuts down grapples and shoves.

Hex is also added to your always-prepared list at Level 10, so it never costs you a prepared spell.

Playstyle Notes

The Great Old One Patron wins by making enemies less capable rather than by out-damaging them.

1. Psychic Spells — convert your damage to Psychic to line up with gear and Mental-condition synergies, and toggle it off against Psychic-resistant enemies
2. Hex + Eldritch Hex — always prepared from Level 10; pick the ability that matters against this enemy
3. Entropic Ward — expensive, so save it for an attack that would genuinely hurt
4. Thought Shield — halves incoming Psychic damage and reflects a point back, which makes mind flayer encounters considerably easier
5. Subtle casting — Enchantment and Illusion spells need no Verbal component and do not break Stealth, which lets you open a fight from concealment