Giving it some tries.
https://chatgpt.com/share/20c2f944-6008-4d05-96d7-cc5d6209707a
Input:
Create me a D&D 5E Subclass. The main class is Rogue The subclass should feel like it is heavily inspired on warlock, combining dextrous melee with eldritch powers. Provide some lore on where these powers come from. Grant features on the same levels as on other Rogue subclasses which can include warlock cantrips and invocations.
Output:
Rogue Subclass: The Eldritch Blade
Lore:
In the world of mysticism and shadows, there exists a clandestine pact between the Rogues and eldritch beings from beyond the mortal realm. These entities, known as the Whispering Shadows, grant their chosen rogues access to otherworldly powers in exchange for their service and secrecy. The rogues who accept this pact become Eldritch Blades, masters of combining their agility and combat prowess with the arcane might of the Whispering Shadows.
The Eldritch Blades are rare and elusive, often operating in the shadows and using their abilities to carry out missions that ordinary rogues would find impossible. Their powers manifest in a blend of swift melee strikes and arcane abilities, making them formidable opponents.
Subclass Features:
Level 3: Pact of the Blade
Upon choosing this archetype at 3rd level, you forge a pact with the Whispering Shadows. This pact grants you the ability to use warlock cantrips and invocations to enhance your combat abilities.
Eldritch Cantrips: You learn two cantrips of your choice from the warlock spell list. They count as rogue cantrips for you, and Charisma is your spellcasting ability for them.
Invocations: You gain one Eldritch Invocation of your choice from the warlock class. You gain an additional invocation at 9th, 13th, and 17th levels. These invocations must be chosen from those available to warlocks and must be invocations that do not have a prerequisite level higher than your rogue level.
Level 9: Shadow Step
At 9th level, you gain the ability to step through the veil between worlds. As a bonus action, you can teleport up to 30 feet to an unoccupied space you can see. If you use this ability to appear in dim light or darkness, you become invisible until the start of your next turn or until you make an attack or cast a spell.
Level 13: Eldritch Strikes
At 13th level, your melee attacks are infused with eldritch energy. When you hit a creature with a melee weapon attack, you can choose to deal additional psychic damage equal to your Charisma modifier (minimum of 1). You can use this feature a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.
Level 17: Whispering Shadows
At 17th level, the Whispering Shadows grant you the ability to blur the line between the material and ethereal planes. As an action, you can become ethereal, as if you had cast the etherealness spell, without expending a spell slot. While in this form, you can use your Shadow Step feature without limitation, and your Eldritch Strikes deal an additional 1d8 psychic damage. This ethereal form lasts for 1 minute or until you end it as a bonus action. Once you use this feature, you can’t use it again until you finish a long rest.
Invocations Suggestions:
Armor of Shadows: You can cast mage armor on yourself at will, without expending a spell slot or material components.
Devil’s Sight: You can see normally in darkness, both magical and nonmagical, to a distance of 120 feet.
Beguiling Influence: You gain proficiency in the Deception and Persuasion skills.
Mask of Many Faces: You can cast disguise self at will, without expending a spell slot.
Thirsting Blade: You can attack with your pact weapon twice, instead of once, whenever you take the Attack action on your turn (requires Pact of the Blade).
This subclass combines the rogue's dexterous combat style with warlock-like eldritch powers, offering a unique playstyle that balances melee combat with magical abilities.