Excalibur

You conjure a legendary holy weapon to strike your foe. On your turn, you speak the blade's name (verbal or non verbal), and conjure a holy weapon of your choice in your hand. When you cast this spell, you can make up to two melee spell attacks with the blade. On a hit, the target takes 4d12 radiant damage. This damage bypasses resistance and immunity. This attack scores a critical hit if the number on the d20 is 18 or higher. On a critical hit, the blade deals an extra 8d12 radiant damage (for a total of 12d12 radiant damage). Creatures who are fiend or undead must in a 60ft radius of the blade must make a constitution saving throw. On a failed save, creatures take an additional 4d12 radiant damage and are blinded. Creatures take half damage on a successful save and are not blinded. 

this blade can not be forcefully disarmed (as it will reappear in the users hand after being knocked down). This weapon can only be wielded by the caster (the weapon will reappear in the casters hand if worn by someone else) and cannot be destroyed. Those wielding the weapon, gain 50 temporary hit points and have advantage on attack roles until the temporary hit point vanishes. The weapon disappears when the user is unconscious. This weapon can pass through any barriers such as Wall of Force and Forcecage