You can use your mastery over your body to transform into anyone or anything you have seen before. Since this is a physical transformation and not a simple illusion, others will have disadvantage on rolls when decerning whether or not you are disguised, with a DC of 12+ your Charisma modifier.

While transformed into an inanimate object, your movement speed is reduced to 10 feet. Others will have to succeed on an investigation check equal to 10+ your Charisma modifier. However, if you move in the line of sight of anyone, that person will have advantage on their investigation roll, unless the object you have transformed into can easily move on its own. (DM's discretion.)

This transformation does not have to be full-body. You could extend a limb, or transform it into a weapon, (1d6 slashing, piercing, or bludgeoning.)

However, you are limited as to how you can control your body. You cannot exceed a 10 foot sphere around you, and you cannot become smaller than 2 inches in any direction.

You can also don and doff armor instantly.

Your biology does not allow you to be poisoned easily, and the ash you are made of grants you a resistance to fire.

You gain a +2 to Charisma up to a maximum of 20, and a +1 in two other stats of your choice.

You can choose a proficiency in a skill, and one feat.

Your demonic heritage grants you the power to see near perfectly in low light conditions. You can see in dim light within 120 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.

You have a base walking speed of 30 feet.

You can sprout wings of ash to fly with a speed of 40feet. However, this ability is not usable while wearing medium or heavy armor, or while overencumbered.

You can speak, read, and write Common, Abyssal, Infernal, and one more language of your choice.