Pact of The Paradox

See above. Does what it says on the tin.

Level 3: Non “Existence”

At 3rd level, A Pact of the Paradox Warlock can choose to no longer exist, or even have existed. As a Bonus Action, and by spending a spell slot, they slip from the perceptions, and memories of all who have ever known them for a number of minutes equal to the spell slot spent. They cannot attack while they do not exist, but can bypass any defenses, including walls, and any other interaction they do will be somehow explained away in the minds of the people who may witness it. When the time runs out, all memories connected to the Player return, excluding anything they did while non-existent. To everyone else, it will appear as if they took forever to teleport.

Schrodinger's Anything

At 6th Level,  A Paradox Pact Warlock has the ability to designate a Medium or smaller nonmagical object within eyesight, and decide whether or not it does exist. This ability can be used as a reaction. Once an object is designated,  a new one cannot be designated without using another charge of the ability. The warlock can use this ability for a number of times equal to their intelligence modifier, and it recharges after a Long Rest.

Existential Anchor

At 10th level, twice per long rest, the Warlock can use their bonus action to rewind their position in time exactly 30 seconds. Any damage they dealt is undone, any damage they took is healed, any spell slots they burnt are returned to them, any class features they used are unused. From the perspective of everyone else, they did not exist for those 30 seconds for which they personally undid for themselves.

Cease With Me

At 14th level, Once per long rest, the warlock, upon using their Non"Existence" Feature, can designate a single creature within eyesight, and force them to cease existing as well. When the other character ceases to exist, if they are unwilling, or unfriendly, they must roll a DC 8 saving throw with no modifiers, and if they fail the check, they cease to exist permanently, not returning to existence with the Warlock. If the targeted creature remains non-existent, This feature will take an extra long rest to recharge.