Gaseous Form is a level 3 transmutation spell. This spell allows spellcasters to transform themselves or an ally into a cloud of mist to avoid attacks, reduce size, and gain Advantage on some Saving Throws.
Description
Transform yourself or an ally into a tiny gas cloud. It can't fall, and fits through small openings. It is very hard to damage.
The description "fits through small openings" includes traveling to different regions by going through small openings (pipes, animal burrows, cat holes, etc.), but also includes moving through 'walls' with openings in them like prison bars and gates.
As a cloud of mist, you also gain the ability to fly.
Contrary to the tooltip, unarmed attacks can be made without losing the form. This deals only the base unarmed damage and may go undetected depending on a Stealth check.
Gaseous Form is a level 3 transmutation spell. This spell allows spellcasters to transform themselves or an ally into a cloud of mist to avoid attacks, reduce size, and gain Advantage on some Saving Throws.
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Advantage on Constitution, Dexterity, and Strength 
Saving throws.
While transformed, the target won't be able to attack[See Notes], cast spells, or talk.
Action + 
Level 3 Spell Slot
Melee: 1.5 m / 5 ft
Duration: Until Long rest 