Construct Infinity

Construct & surround yourself with "Infinity", granting a +6 bonus to AC and also forcing any and all objects/attacks to gradually slow down as they approach you; functionally recreating the Achilles paradox.
This means you are unable to be hit by normal means.

This affects all attacks that need to travel distance to reach you, meaning certain spells like Banishment can bypass it, meaning you cannot be healed or buffed while this is active.
This is also countered by Dispel Magic and Counter Spell.

If someone manages to hit the user's AC or gets a critical success when rolling to hit, the user is hit with a -1 to their bonus AC from infinity & must perform a constitution saving throw to maintain their infinity to keep the attack from reaching them. If the user fails, they will lose 2 spell slots & an action on their next turn, and the attacker will gain an advantage on their next attack roll against the user. If the user succeeds, they will instead only lose a bonus action.

Each turn, you can chose whether or not you want to disable this or not. If you don't, you will automatically expend 1 spell slot to keep infinity enabled. This does not cost an action or bonus action.
If there are no spell slots left, gain a level of exhaustion instead.

This also has a unique interaction with the "Eversong" dagger, whereas if the user is hit through infinity with it, they will suffer a bonus 1d6 psychic damage.

At Higher Levels. When casted with a 4th level spell slot or more, this can be casted with specific whitelisting/blacklisting system, where it will automatically distinguish between friend and foe, allowing you to be buffed or healed while active.