When you offer yourself up to an eldritch horror, you can expect your brain to melt a little. Some madness might seep in. But the joy of such a pact is you get to pass that trauma onto your enemies by holding their hopes, dreams, and deepest fears in a vice grip you use to enslave their minds! Hooray!
Serving a Great Old One patron doesn’t make you much better in combat than any other Warlock. Most of this subclass is about flavor and roleplay. Synergizing with the subclass features that let you read minds or twist someone’s thoughts is how you’ll get the most fun from Great Old One.
So if you’re tired of winning combat by stabbing the bugbear and would much rather make its daddy issues resurface as a way to take it out of the fight, this subclass should be right up your alley.
Using This Guide
Everything in this guide has an emoji, ranking how useful a given ability or feature is to playing this class effectively.
✅ — An absolutely crucial feature. Often forms the backbone of a class’ look and feel. Will provide some bonus that can’t be found through other means.
🆗 — A solid feature that does its job well. Not game-breaking, and certainly replaceable, but a strong choice that shores up some weakness.
⚠️ — A debatable choice. Could work for a specific build, but otherwise is either a wasted opportunity or is just weaker than other alternatives.
⛔ — Outright bad and detrimental. This weighs down the class and just takes up space on the character sheet. A weakness you will have to accommodate for.
These rankings are meant to help you create an optimized class build but remember—DnD isn’t a game where you need to win to have fun. Weaker but flavorful builds also have their place and can make for fulfilling characters.
How To Play A Great Old One Warlock
While you need to choose the right moment to spend your spell slots just like any Warlock, this subclass leans into its spellcasting side. A number of your subclass features and spells synergize well to get under your target’s skin, laying the groundwork for some roleplay that can solve problems without escalating them to all-out combat.
When a fight does start, you should default to using eldritch blast to pick off injured enemies. When the time is right, use a spell slot for a big effect that will weaken or debuff serious threats (Controlling). Outside of combat, you can put those spell slots to good use as a toolkit for your party (Utility Casting).
A number of your subclass features also make you better at diplomacy, intimidation, and overall roleplay. Use these features to become the party’s face and do all the talking. Pick spells which make this easier, often by creating illusions to baffle targets or by casting spells which charm and frighten them.
Being An Effective Controller
Rather than killing enemies, you want to incapacitate or slow them down so that another party member can bring the pain. This warlock subclass specializes in single-target control spells meant to take out one big enemy, so aim at the scariest monster on the battlefield and hope your concentration holds. You also get access to a few good mind control effects, which are even better. Removing a threat while also gaining an ally is invaluable.
Great Old One struggles with big crowds, so whenever possible, pick up area-of-effect spells. Use these to disable groups of enemies at once or to create obstacles on the battlefield that will slow them down. Sometimes, your best option will be to save the spell slot if the situation isn’t right (in these moments, turn to eldritch blast).
Being An Effective Utility Caster
Utility casting is using spells for non-combat effects. These include effects like tracking magical sources or mind reading. Your subclass features grant you a few good utility effects, so build on those. Avoid overlap, both with yourself and with other spellcaster party members.
As a Warlock, you have a very limited number of spell slots per day, so look for ways to pick up extra spells. Your Eldritch Invocations are perfect for this, and some feats and racial traits aren’t half bad either. Be sure to spend your spell slots on utility effects only when you can take a short rest before getting into combat to avoid being left high and dry.
Great Old One Subclass Features
If you want the perfect intersection of gameplay and roleplay, this is the subclass for you. A Great Old One Warlock gets a number of subclass features that make you good at twisting your enemies’ minds into a mental headlock. You can use these to help take control of a fight, or just use them as fun flavor to spook goblins.
🆗 Expanded Spell List
🆗 Dissonant Whispers
The damage scales well, and making the target move away from you means this spell is perfect for when a baddie flanks your party and gets up in your face. However, this is the first of many spells Great Old One gets that require repeated failed Wisdom saves in order to stick (a Wisdom-save-or-suck if you will, or WSoS for short). If you learn too many, you become reliant on them which will backfire when facing an enemy with high Wisdom, so that inflexibility makes them worse.
🆗 Tasha’s Hideous Laughter
WSoS. This is as close as you’ll get to taking something completely out of the fight while the spell is affecting them. Prone, incapacitated, unable to stand up, and laughing like mad makes the biggest threat on the battlefield a joke.
🆗 Detect Thoughts
Mind reading! You already get telepathy with the subclass, so the only other use of this spell is lie-detecting the target. Ask a question, and the mind reading should give you the answer as they think it through, even if they proceed to lie to your face. That’s an okay effect, but pretty limited.
✅ Phantasmal Force
Climbing into a target’s mind and planting an illusion Inception-style offers so many possibilities. My favorites include trapping the target in a ball of fire or resurrecting a dead relative. You can do so much that this is totally worth the spell slot.
A magical security camera is just as useful as you’d think it would be. Unfortunately, the 10 minute duration bites. You can get an Invocation in the late game granting you the arcane eye spell, which is the better version of this.
Even if you were allowed to send more than 25 words at a time, that wouldn’t be a big enough effect to warrant the wasted spell slot this takes. If you want this kind of effect, read up on the Far Scribe Invocation using this guide from dnd5e.wikidot for a better alternative.
⚠️ Dominate Beast
WSoS. Snagging the scariest enemy like it was a Pokemon can turn the tides in a battle. However, there aren’t that many beasts, so your list of allowed targets is comparatively small. And most beasts are pretty puny creatures. And your victim will get frequent saves to break the spell if you use this in combat.
✅ Evard’s Black Tentacles
Difficult terrain? Check. Damage? Check. Restrained? Check. This spell covers a wide area and is very good at disabling anything that passes through its radius. A perfect roadblock to drop in combat against a bunch of small enemies that can’t fly.
🆗 Dominate Person
WSoS. You run into humanoids all the time, and the vast majority of spellcasting enemies are humanoids. This spell therefore has a lot of viable targets, and mind-controlling one will usually have a bigger effect than casting dominate beast to grab a glorified donkey. The beauty is you can both disable an enemy and gain a powerful ally with one spell. Just be careful of how easily your control can slip.
The better mage hand! You get all the utility uses like opening doors, unlocking chests, and a hefty 1000 pounds of weight that you can drag around. Compliment that with the ability to at worst restrain an enemy for a round and at best drop them mid-air… that’s a pretty good deal. And being able to fling stuff around for the full concentration duration makes this an efficient use of your spell slots.
✅ Awakened Mind
Telepathy is great for playing mind games, which the flavor of this subclass will help you do very well. But the real star of this show is being able to communicate with anything regardless of the language barrier. For a class with such high Charisma, that makes talking your way out of danger much easier.
🆗 Entropic Mind
When you need a quick defensive buff to avoid dying to a big monster, this really comes in handy. Getting advantage on your next attack is nice but not incredible (it’ll probably be eldritch blast, which uses so many attack rolls that getting advantage on one is minimal). Nothing to complain about here, but save this ability for the right moment.
⚠️ Thought Shield
Psychic damage is not common at all, so although a damage resistance is nice, this is the most useless one to get. Not having your thoughts read is the same problem: way too niche to make this feature anything better than “okay”.
⚠️ Create Thrall
Have a read through your Player’s Handbook’s section on “Conditions” and you’ll understand why this ability is rated so low. Charming something does little more than stop it from stabbing you, and not that many effects incapacitate something. You’re best off using this ability on someone who is sleeping soundly in their bed. It’s certainly fun flavor and can grant you a useful ally, but you have to jump through a lot of hoops, which isn’t what you want from the final capstone ability of a subclass.
The Perfect Great Old One Build
Picking up the ability to cast as many spells as possible helps you be the best spellcaster you can be. Also look for ways to improve your defenses, especially effects that help you maintain concentration on your spells.
Focus mainly on either Dexterity or Constitution, depending on how you like to play defensively. Either a high AC or high health will keep you alive longer, but you probably don’t have enough ability score increases to balance both. Specialize to survive.
See Dexterity. More health is always better, as is a strong saving throw to maintain concentration.
The Great Old One subclass is reliant on its spells, and many of those are opposed by simple saving throws. Cranking up your Charisma is crucial to getting a high spell save DC so your spells actually stick. Some of your subclass abilities also encourage roleplay and diplomacy, so you will likely end up as the party’s face, which also needs high Charisma to pull off.
✅ Having an ever-changing disguise as a Changeling can help you get inside your enemies’ heads. Similarly, the spells Baalzebul, Dispater, Fierna, and Glasya Tieflings get are great for either mental mischief or utility casting. More good options include Eladrin, Half-Elf, Satyr, Verdan, Warforged, or Yuan-Ti Pureblood.
🆗 Aasimar, Simic Hybrid, Tabaxi, Triton, and Variant Human are solid alternatives which help buff your defense while including the crucial Charisma boost you want from your race.
🆗 Moderately Armored
More armor, less problems. Though you can skip this if you’re dexterous enough.
🆗 Ritual Caster
Similarly to the Book of Ancient Secrets Invocation, this grants you a few spells to cast as rituals. Having an expanded spell list never hurts, and as a utility caster, you can pick up some pretty useful rituals that your party might not otherwise have access to.
✅ War Caster
Many of your Wisdom-save-or-suck spells will require concentration to maintain, so this feat is crucial to getting the most out of your spell slots. Nobody wants to mind control the bugbear king only for them to shrug it off next turn because you are stepping on a spike trap. Additionally, shooting an eldritch blast as an opportunity attack is wonderful.
✅ Agonizing Blast
Eldritch blast is an important fallback for when there’s nothing better to spend your turn on. Pumping up its damage is a no-brainer.
🆗 Book of Ancient Secrets
Getting to cast more rituals expands your role as a utility caster. You can round out your arsenal nicely with a few good picks to fill the gaps in your party’s utility options.
✅ Eldritch Mind
Great Old One Warlock is very susceptible to wasting spells from broken concentration. Pick up as many bonuses to concentration checks as possible, starting with this one.
✅ Mask of Many Faces
Disguise yourself for fun and profit. This ties in well with the subclass’ other abilities which let you mess with someone’s head.
✅ Misty Visions
If you get creative with this, silent image is one of the most versatile spells in the game. Some aggressive roleplay paired with this spell can drive enemies insane, make interrogations a breeze, or immobilize a crowd.
Warlock Pact Boons
Great Old One Warlock likes their spells, so Pact of the Tome is the best choice. Your top picks for cantrips will be things like guidance, light, shillelagh, thaumaturgy, or toll the dead. Or you can always take a Warlock cantrip you didn’t have room for. To browse through all the possible options for cantrips, check out this comprehensive list from D&DBeyond.
Pact of the Tome has some crappy Invocations, but Book of Ancient Secrets is definitely worth picking up. Rituals like detect magic, identify, and unseen servant improve your role as a utility caster, and being able to write down new spells on your adventures means you can fill out your spell list and always have the right tool for the job. Gift of the Protectors is another useful Invocation that can keep your party from dying in combat.
If magic books aren’t your style, Pact of the Chain isn’t a bad alternative. Getting a familiar to use for recon or to guard you in combat helps you win fights. Pact of the Talisman can also help keep you alive with its bonus dice. The only outright bad option is Pact of the Blade, which works counter to what Great Old One is trying to do.
✅ Eldritch Blast
Excellent damage and range make this essential for Warlock.
🆗 Mage Hand
The ability to grab things from afar saves you a lot of trouble, from disarming traps to picking pockets.
✅ Minor Illusion
Illusion spells are perfect to trick your enemies into acting in their own disinterest. Minor illusion might be small, but you have to start somewhere, and having it as a cantrip means you always have the option to whip up a quick illusion.
✅ Armor of Agathys
The undisputed king of Warlock’s defensive spells. It scales well, it soaks up damage, it hurts attackers. Is there anything it doesn’t do?
🆗 Mirror Image
For a single casting, you get an incredible defensive bonus that will last multiple turns. Your poor AC and health won’t matter if attacks never hit you.
The perfect multipurpose mind control. With clever phrasing, most actions can be boiled down to a one-sentence command. This is basically the better version of the charmed condition.
🆗 Enemies Abound
While it doesn’t debilitate a target, you will likely cause some infighting amongst your enemies. If you hit the biggest creature, they might even be able to kill some of their friends before the spell ends.
✅ Hunger Of Hadar
Incredible battlefield control spell. This will slow down enemies, block line of sight, and deal damage, meaning wherever you drop this becomes an absolute slog for bad guys to fight through.
✅ Major Image
Bigger illusions mean bigger effects. And getting the ability to create a moving image opens up many new doors. If used wisely, there is almost no way for someone to see through this illusion unless the spell ends suddenly.
🆗 Hallucinatory Terrain
Definitely not the strongest spell, but screwing with someone’s head is just so much fun, and in-line with this subclass’ flavor. I personally recommend making someone think the floor around them is an endless free fall into a volcano. Very good intimidation.
Climbing inside somebody’s dreams is exactly the kind of shenanigans this subclass likes to pull. Excellent flavor with an almost unlimited range.
✅ Modify Memory
More mental madness! Magically gaslighting someone is super useful during roleplay, but can also cripple an enemy in combat, even making them turn on their friends.
✅ Synaptic Static
Excellent area-of-effect damage with the added bonus of weakening everyone affected, making it easy to mop up whatever survives this spell’s damage.
🆗 Mass Suggestion
Both an upgrade over suggestion in terms of duration and number of targets. A very efficient use of a Mystic Arcanum spell, as you can create some pretty big effects.
✅ Mental Prison
Aside from the initial damage, this either immobilizes a target or deals a ton more damage. Whichever outcome, this is the perfect way to debilitate a scary monster.
With some maneuvering, you can trap a lot of baddies at once. The cage itself can also act as an obstacle, meaning this spell does double-duty as a control option.
✅ Dominate Monster
Great Old One already gets dominate beast and dominate person, so this rounds out your arsenal, leaving nothing you can’t mind control.
Leaving a spellcaster impotent can easily turn the tide of a battle and makes them incredibly easy to finish off with a few good dagger thrusts.
🆗 Maddening Darkness
Great to drop in a room and leave to do its work. The darkness blocks line of sight and confuses enemies, while the damage is pretty good and might help drive a few people insane.
This is such a massive bonus. Cast it on yourself, cast it on a friend, but just cast it. Very hard to go wrong here.
✅ True Polymorph
Such a versatile spell. This subclass in particular might enjoy messing with people by inflicting permanent transformations. A few extra tentacles never hurt.
You’re not a fighter, and your proficiencies reflect that. The best option for armor is studded leather for the biggest AC bonus.
Should you find yourself on the front lines of a scrap, you’ll want a weapon on-hand, though you only get access to simple weapons. For maximum damage, snag a handaxe, javelin, mace, quarterstaff, or spear, and if you are willing to fight two-handed, a greatclub.
Your ranged weapon options are no better than a good eldritch blast, but if magic isn’t an option, a light crossbow is best.
This guide should have given you a good idea of just how weird and wonderful Great Old One Warlocks can be. Leave a comment telling us the story of the wackiest mental mayhem your Warlock caused. And if you found this guide helpful, share it with your friends!