Become Shadow v

The caster utters a few arcane words and performs a few gestures, appearing to lose their consistency and becoming less defined as they do so, finally becoming a dark, nebulous mist once the spell is fully cast, reminiscent of a shadow, with two red pinpricks of light resembling eyes. In this state, the caster is able to fully alter their selves and are completely gaseous, thereby being able to squeeze through the tightest of cracks or become so diffuse as to be unnoticeable to lookers-on. In this state, the caster is immune to any physical damage, but can still be affected by magical attacks that require saving throws, Magical effects, and psychic damage. Once the time limit is reached, the gas that is the caster collects and congeals, solidifying back into their original state (will suffer injury at the DM's discretion if partially in an object, e.g. a door)