Bone Cocoon

Steinhardt's Guide to the Eldritch Hunt

Bone Cocoon

2-level Abjuration

Casting Time: 1 reaction, which you take when you see a creature drop to 0 hit points

Range/Area: 30 feet

Components: V, S, M (a shrunk and gilded rib cage worth at least 50 gp)

Duration: Concentration, up to 1 minute

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.

Available for: Druid, Sorcerer, Warlock, Wizard