Ultra Instinct

You enter a mental state of complete nothingness, allowing your body to move out of danger on it's own.
For the duration of the spell you count as Feeble-Minded, except you retain the ability to keep your concentration on the Ultra Instinct spell or drop it at will.

Your base AC becomes 30 for the duration or until you loose concentration.
If your base AC already was 30 or higher, you instead gain +5 AC for the duration.
You automatically succeed on dexterity and wisdom saves,
as well as having advantage on constitution, strength and charisma saves.
Enemies can not take attacks of opportunity against you.
Physical attacks always count as if you had rolled a natural 20 on your attack roll, the damage roll stays unaffected however.

After the spell ends, you must make a DC 20 constitution saving throw against the aftereffects:
-On a critical fail your hit-points are reduced to 1 and you take 4 levels of exhaustion.
-On a fail you take 5d6 force damage and you take 2 levels of exhaustion.
-On a success you take 2d8 force damage and you take 1 level of exhaustion.
-On a critical success you simply take 1d8 force damage.

When cast with an 8th level spell slot:
-The saving throw for the aftereffects becomes a DC 10 constitution saving throw.
-If you roll a natural 1 on the saving throw against the aftereffects, treat the roll as a natural 2 instead.
-For the duration your base AC is 40 instead of 30 (or +10AC if it already was 40 or higher).

When cast with a 9th level spell slot:
-You gain the effects of casting with an 8th level spell slot.
-You are no longer Feeble-Minded for the duration, but can only cast spells up to and including level 3.
-You now additionally gain advantage on intelligence saving throws.