Compendium of Forgotten Secrets - Awakening
Umbral Form
3-level Transmutation
Casting Time: 1 action
Range/Area: Touch
Components: V, S, M
Materials: a drop of black ink
Duration: Concentration, up to 1 hour
You transform a willing creature you touch, along with everything it's wearing and carrying, into an animated shadow for the duration. The spell ends if the creature drops to 0 hit points.
While in this form, the target has an AC of 18, its only method of movement is a walking and climbing speed of 20 feet, and it cannot jump or otherwise remove itself from the surface it moves on. This movement is completely noiseless, and allows the target to move up, down, and across vertical surfaces and upside down on ceilings. The target can enter and occupy the space of another creature. It has advantage on Dexterity saving throws, Dexterity (Stealth) checks, and is always hidden in darkness. The target can pass through small holes, narrow openings, and even mere cracks, though it treats liquids as though they were solid surfaces. The target can't fall and remains on the surface it was on even when stunned or otherwise incapacitated.
While in the shadowy form, the target can't talk or manipulate objects, and any objects it was carrying or holding can't be dropped, used, or otherwise interacted with. The target can't attack or cast spells.