Blazing Bones

Illumination. The Blazing Bones sheds either dim light in a 15-foot radius, or bright light in a 15-foot radius and dim light for an additional 15 feet. It can switch between the options as an action.

Magic Resistance. The  Blazing Bones has advantage on saving throws against spells and other magical effects.

Rejuvenation. If the  Blazing Bones is destroyed, it regains all its hit points in 1 hour unless Holy Water is sprinkled on its remains or a dispel magic or remove curse spell is cast on them.

Spellcasting. The Blazing Bones is a 8th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 14, +6 to hit with spell attacks). It requires no somatic or material components to cast its spells. The Blazing Bones has the following wizard spells prepared:

Cantrip (at will): mage hand

1st level (4 slots): magic missile, shield

2nd level (3 slots): blur, flaming sphere, Scorching Ray

3rd level (3 slot): fireball, flame arrow

4th level (2 slots): Wall of Fire

Multiattack. The flameskull uses Fire Ray twice OR one Burning Whirlwind

Fire Ray. Ranged Spell Attack: +5 to hit, range 30 ft., one target. Hit: 10 (3d6) fire damage.

Unarmed Strike. melee attack: +4 to hit, range 5ft, one target. hit: 3(1d4+1) bludgeoning damage and 12(4d6) fire damage

Burning Whirlwind. all creatures within a 30ft cone area must make a dexterity saving throw. (DC 14) on a fail they take 6d6 fire damage and are knocked back 20ft and prone.