Your Patron is a lord or lady of the fey, a creature of legend who holds secrets that were forgotten before the mortal races were born. This being's motivations are often inscrutable, and sometimes whimsical, and might involve a striving for greater magical power or the settling of age-old grudges.
Archfey Expanded Spells:
1st Level Spells: Faerie Fire, Sleep
2nd Level Spells: Calm Emotions, Phantasmal Force
3rd Level Spells: Blink, Plant Growth
4th Level Spells: Dominate Beast, Greater Invisibility
5th Level Spells: Dominate Person, Seeming
Fey Presence: Starting at 1st level, your Patron bestows upon you the ability to project the beguiling and fearsome presence of the fey. As an action, you can cause each creature in a 10-foot cube originating from you to make a Wisdom saving throw against your warlock spell save DC. The creatures that fail their saving throws are all charmed or frightened by you (your choice) until the end of your next turn. Once you use this feature, you can't use it again until you finish a short or long rest.
Misty Escape: Starting at 6th level, you can vanish in a puff of mist in response to harm. When you take damage, you can use your reaction to turn invisible and teleport up to 60 feet to an unoccupied space you can see. You remain invisible until the start of your next turn or until you attack or cast a spell. Once you use this feature, you can't use it again until you finish a short or long rest.
Beguiling Defenses: Beginning at 10th level, your Patron teaches you how to turn the mind-affecting magic of your enemies against them. You are immune to being charmed, and when another creature attempts to charm you, you can use your reaction to attempt to turn the charm back on that creature. The creature must succeed on a Wisdom saving throw against your warlock spell save DC or be charmed by you for 1 minute or until the creature takes any damage.
Dark Delirium: Starting at 14th level, you can plunge a creature into an illusory realm. As an action, choose a creature that you can see within 60 feet of you. It must make a Wisdom saving throw against your warlock spell save DC. On a failed save, it is charmed or frightened by you (your choice) for 1 minute or until your concentration is broken. This effect ends early if the creature takes any damage. Until this illusion ends, the creature thinks it is lost in a misty realm, the appearance of which you choose. The creature can see and hear only itself, you, and the illusion. You must finish a short or long rest before you can use this feature again.
You have made a pact with a fiend from the lower planes of existence, a being whose aims are evil, even if you strive against those aims. Such beings desire the corruption or destruction of all things, ultimately including you.
Fiend Expanded Spells:
1st Level Spells: Burning Hands, Command
2nd Level Spells: Blindness/Deafness, Scorching Ray
3rd Level Spells: Fireball, Stinking Cloud
4th Level Spells: Fire Shield, Wall of Fire
5th Level Spells: Flame Strike, Hallow
Dark One's Blessing: Starting at 1st level, when you reduce a hostile creature to 0 hit points, you gain temporary hit points equal to your Charisma modifier + your warlock level (minimum of 1).
Dark One's Own Luck: Starting at 6th level, you can call on your patron to alter fate in your favor. When you make an ability check or a saving throw, you can use this feature to add a d10 to your roll. You can do so after seeing the initial roll but before any of the roll's effects occur. Once you use this feature, you can't use it again until you finish a short or long rest.
Fiendish Resilience: Starting at 10th level, you can choose one damage type when you finish a short or long rest. You gain resistance to that damage type until you choose a different one with this feature. Damage from magical weapons or silver weapons ignores this resistance.
Hurl Through Hell: Starting at 14th level, when you hit a creature with an attack, you can use this feature to instantly transport the target through the lower planes. The creature disappears and hurtles through a nightmare landscape. At the end of your next turn, the target returns to the space it previously occupied, or the nearest unoccupied space. If the target is not a fiend, it takes 10d10 psychic damage as it reels from its horrific experience. Once you use this feature, you can't use it again until you finish a long rest.
Your patron is a mysterious entity whose nature is utterly foreign to the fabric of reality. It might come from the Far Realm, the space beyond reality, or it could be one of the elder gods known only in legends. Its motives are incomprehensible to mortals, and its knowledge so immense and ancient that even the greatest libraries pale in comparison to the vast secrets it holds. The Great Old One might be unaware of your existence or entirely indifferent to you, but the secrets you have learned allow you to draw your magic from it.
Great Old One Expanded Spells:
1st Level Spells: Dissonant Whispers, Tasha's Hideous Laughter
2nd Level Spells: Detect Thoughts, Phantasmal Force
3rd Level Spells: Clairvoyance, Sending
4th Level Spells: Dominate Beast, Evard's Black Tentacles
5th Level Spells: Dominate Person, Telekinesis
Awakened Mind: Starting at 1st level, your alien knowledge gives you the ability to touch the minds of other creatures. You can telepathically speak to any creature you can see within 30 feet of you. You don't need to share a language with the creature for it to understand your telepathic utterances, but the creature must be able to understand at least one language.
Entropic Ward: At 6th level, you learn to magically ward yourself against attack and to turn an enemy's failed strike into good luck for yourself. When a creature makes an attack roll against you, you can use your reaction to impose disadvantage on that roll. If the attack misses you, your next attack roll against the creature has advantage if you make it before the end of your next turn. Once you use this feature, you can't use it again until you finish a short or long rest.
Thought Shield: Starting at 10th level, your thoughts can't be read by telepathy or other means unless you allow it. You also have resistance to psychic damage, and whenever a creature deals psychic damage to you, that creature takes the same amount of damage that you do.
Create Thrall: At 14th level, you gain the ability to infect a humanoid's mind with the alien magic of your patron. You can use your action to touch an incapacitated humanoid. That creature is then charmed by you until a Remove Curse spell is cast on it, the charmed condition is removed from it, or you use this feature again. You can communicate telepathically with the charmed creature as long as the two of you are on the same plane of existence.