Worrgrendel
Adventurer
Invulnerability: This means that you can cast a spell and enter an object in the same turn to get the benefit of full cover.
You may still have resistance against radiant damage being aasimar.
In practice, you are invulnerable.
Correction. You are not invulnerable. You are resistant. Invulnerable you take zero damage. Resistant you take half. Which is still damage.
I back to the fight every turn: You can wish for duplicate Regenerate spell that means that you can't be defeated by damage for 1 hour. (Regaining 1 hp per turn, you back to fight each turn even if you are reduced to 0 hp)
You can also apply twin spell on Simulacrum (Via wish) for still more power.
The Shadow Lord casts Distant Empowered Dark Star for 300ft range (Casting via Subtle Wish). The enemies can't cast spells with verbal component and It's blind and deaf.
Also, this is 3 castings of Wish. You only get 1 9th level spell slot per day so I'm not sure how you are accomplishing this.
I back to the fight every turn: You can wish for duplicate Regenerate spell that means that you can't be defeated by damage for 1 hour. (Regaining 1 hp per turn, you back to fight each turn even if you are reduced to 0 hp)
Incorrect. While you regain 1 hp at the start of your turn you can still fail death saves while you are unconscious and die as a result of that.
Damage at 0 Hit Points: If you take any damage while you have 0 hit points, you suffer a death saving throw failure. If the damage is from a critical hit, you suffer two failures instead.
While you are unconscious any hit against you within 5 feet of you is an automatic critical so once you go down only 2 hits are required to kill you outright regardless of damage and regeneration.
You remain in this form for 1 minute. It ends early if you are incapacitated, if you die, or if you dismiss it as a bonus action.
Additionally, once you go unconscious you become incapacitated. When you are incapacitated you lose Umbral Form.