Bone Cocoon

You conjure a cocoon made of cartilage and bones, which protects the creature that dropped to 0 hit
points. While in the cocoon, the creature can’t be damaged by attacks or effects originating from outside, has total cover, is considered restrained, and makes death saving throws at advantage.

The cocoon has 25 hit points and an AC of 11 + your spellcasting ability modifier. It has resistance to cold, fire, and necrotic damage, and immunity to poison and psychic damage. If you lose concentration or the cocoon is reduced to 0 hit points, it is destroyed.