Ability Score Increase. +2 Con, -2 Cha
Creature Type. You gain the Undead tag.
Resistances. Necrotic, Poison
Persistent Alignment. Always Lawful Good. If your alignment changes, you die.
Deathless Nature. You don't need to breathe air, eat food, or drink water.
Darkvision. You can see in dim light within 60 feet of you as if it were bright light and in darkness as if it were dim light. You discern colors in that darkness as shades of gray.
Breath Weapon. When you take the Attack action on your turn, you can replace one of your attacks with an exhalation of blue magical energy in a 30-foot line that is 5 feet wide. Each creature in that area must make a Dexterity saving throw (DC = 8 + your Constitution modifier + your proficiency bonus). On a failed save, the creature takes an amount of radiant damage equal to 1d4 + your Constitution modifier. On a successful save, it takes no damage. This damage increases by 1d4 each time you level up (2d4 at 2nd level, 3d4 at 3rd level, etc.). You can use your Breath Weapon a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.
Undead Fortitude. If damage reduces you to 0 hit points, you must make a Constitution saving throw with a DC of 5 + the damage taken. On a success, you drop to 1 hit point instead.