Cinder Swarm

Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a Tiny insect. The swarm can't regain hit points or gain temporary hit points.

Fiery Presence. At the start of each of the swarm's turns, each creature within 15 feet of it takes 35 (10d6) fire damage, and flammable objects in the aura that aren't being worn or carried ignite. A creature also takes 35 (10d6) fire damage from touching the swarm or from hitting it with a melee attack while within 10 feet of it, and a creature takes that damage the first time on a turn that the swarm moves into its space. Nonmagical weapons that hit the swarm are destroyed by Cinders immediately after dealing damage to it.

Illumination. The swarm sheds bright light in a 120-foot radius and dim light in an additional 120 ft. 

Voracious. Any creature that is reduced to 0 hit points by the swarm and is made of flesh is devoured by the billions of Cinders that make up the swarm. The devoured creature and everything it is wearing and carrying, except Magic Items, are eaten by the Cinders, leaving no remains. The creature can be restored to life only by means of a True Resurrection or a wish spell.

Burnt Out. The swarm's abilities that deal fire damage do half damage if the swarm has half of its hit points or fewer.

Overrun. The swarm moves up to 30 feet and into a creature's space and the creature must make a DC 23 Constitution saving throw. The creature takes 62(15d6+10) fire damage and moves 15 feet in a random direction if it can move and its speed is at least 15 feet on a failed save. On a successful save, the target takes half as much damage and only moves up to 5 feet. This movement doesn’t provoke opportunity attacks, and if the direction it moves is blocked, the creature doesn't move.

Scintillating Burst (2/Day) (Recharge 6). The swarm spirals and compacts into a 10-foot dome and stops glowing- allowing enough time for every creature to move up to half their movement speed- before creating a massive burst of light. Each creature in a 100-foot sphere centered on the swarm must make a DC 23 Constitution saving throw -with disadvantage if they are within 20 feet. On a failed save, the creature takes 104(27d6+10) radiant damage, pushed up to 10 feet away from the swarm, and is blinded and deafened for a minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. On a successful save, a creature takes half as much damage and isn't blinded and deafened. If a creature is within 5 feet of the swarm and fails the saving throw, they are blinded until they are targeted by a greater restoration or heal spell.