The Outsider

1st: longstrider, silent image
2nd: find traps, void gaze*
3rd: haste, lure*
4th: domino*, freedom of movement
5th: mislead, modify memory
In addition, you may take stop time as your Mystic Arcanum spell at 17th level.
*custom spells
 

Starting at 1st level, you can spend a bonus action on your turn to move to a point within 10 feet. This movement is impossibly fast and does not provoke attacks of opportunity. You then have advantage on the first weapon attack you make before the end of your turn.

You can also use this ability to pass through a creature's line of sight without being spotted. When moving through spaces a creature can see, they must make a Wisdom (Perception) check against your spell save DC to see you move.

You can use this ability a number of times equal to your Charisma modifier (minimum of 1) before you must complete a short or long rest.

Starting at 6th level, you can momentarily alter a creature's perception to make yourself invisible to them. As a reaction, you can choose a number of creatures equal to your Charisma modifier within 60 feet to be unable to see you until the end of your next turn or you make an attack against them. While the creature is affected by this, it has disadvantage on attacks against you and cannot percieve you without truesight. Creatures that can't be charmed are immune to this effect.

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

Starting at 10th level, you can attempt to take control of another creature's body for a short time. As an action, you can choose a creature you can see within 10 feet to possess for a number of rounds equal to half your warlock level rounded down. The target must make a Charisma saving throw against your spell save DC or be possessed. The target has disadvantage on the save if you are hidden. Targets with an Intelligence of 4 or less automatically fail the saving throw.

While possessing a creature, your body and equipment are absorbed into the target for the duration and they have no control of any actions they take. You cannot talk or take the Dash action in this form or perform complex actions like casting spells. You can end the possession early as a bonus action. If the possessed creature takes damage, you take an equal amount that cannot be avoided or reduced. If you or the possessed creature drop to 0 hit points, you also drop to 0 hit points and this effect ends.

When this effect ends, you and your equipment are placed in a space of your choice within 5 feet of the creature. The creature is left stunned for 1 round and has no recollection of events that occurred while it was possessed.

Once you use this feature, you must complete a short or long rest before you can use it again.

Starting at 14th level, you can transform into a living shadow that sneaks from place to place unseen. As an action, you can meld yourself and any equipment you carry into your own shadow for 1 minute or until you leave it as a bonus action.
While in your shadow form, you cannot cast spells, take the Dash action, or be detected by blindsight and make no sound. You are invisible while in darkness and creatures without darkvision cannot see you in dim light. Your AC is unaffected by any armor you wear and you are vulnerable to radiant damage. Whenever you take any damage, you immediately revert to your normal form.
You can make an attack against a creature within 5 feet using an attack roll equal to 1d20 + your Charisma modifier + your proficiency bonus which deals 6d6 piercing, slashing, or bludgeoning damage (your choice) that is considered magical for the purposes of overcoming resistances and immunities. You then immediately revert to your normal form.
Once you use this feature, you can’t use it again until you finish a long rest.