Your lineage stems from a dragon progenitor. Choose the kind of dragon from the Draconic Ancestors table. Your choice affects your Breath Weapon and Damage Resistance traits as well as your appearance.

When you take the Attack action on your turn, you can replace one of your attacks with an exhalation of magical energy in either a 15-foot Cone or a 30-foot Line that is 5 feet wide (choose the shape each time). Each creature in that area must make a Wisdom saving throw (DC 8 plus your Constitution modifier and Proficiency Bonus). On a failed save, a creature takes 1d10 Psychic or Necrotic damage. On a successful save, a creature takes half as much damage. This damage increases by 1d10 when you reach character levels 5 (2d10), 11 (3d10), and 17 (4d10).

You can use this Breath Weapon a number of times equal to your Proficiency Bonus, and you regain all expended uses when you finish a Long Rest.

You have Resistance to the damage type determined by your Draconic Ancestry trait and Necrotic damage for being Undead.

You have resistance to Necrotic Damage. You are vulnerable to Radiant Damage.

You can momentarily become incorporeal. As a bonus action, you can move through creatures and objects as if they were difficult terrain until the end of your turn. If you end your turn inside an object, you are immediately shunted to the nearest unoccupied space and take 1d10 force damage.

You can use this ability a number of times equal to your proficiency bonus per long rest.

You are bound to undeath by some unfinished business, and memories of you previous life haunt you. Upon completing your business, you die permanently, and your spirit passes on. 

However, until you do so objects of significance from your former life fill you with dread and make you more vulnerable. These objects might be favorite possessions, the instruments of your untimely demise, or even a person of great significance from your former life. These objects must be presented in a way which is specifically traumatic to you, such as torture implements laid out in a torture chamber, a former lover in the company of a rival, or a favored possession in the hands of a thief.

Alternatively, a creature can spend their action to hold the object aloft, forcing you to suffer this vulnerability while they continue to do so. While vulnerable this way, you have vulnerability to all damage types. In addition, if you are reduced to 0 hit points, you are immediately destroyed. If you are already at 0 hit points when you are made vulnerable, you are not immediately destroyed, but suffering any damage in this state immediately destroys you.