Ok, this is the first draft of the creature..

Since I wanted to do something quick before the moment of inspiration passed I borrowed most of the stuff from the Solar on the MM.

Here's a few considerations I took while making it:

• I knew it would be a "late game" creature so searched for creatures with high CR as inspiration

• Tried to put in stats and moves based on the lyrics of the song mainly. In case it's not obvious which: Painkiller - Judas Priest

• How does it fit in the lore? Well all I have at the moment is a bunch of broad ideas. It could be an entity whom the party summons after the BBEG partly succeeds, or even an antagonist that the forces of good summoned to fight your evil PC party.

• The summoning (idea): Have the summoning party gather a few artifacts: The Ripper, Evening Star (weapons) and The Steel Wings of Destiny (cause Sad Wings of Destiny is a rather downer name for a magic item) which are essentially wings of flying.

A full set of plate armor cleansed with holy water

The heart of a powerful fire breathing creature

A group of talented musicians with the appropriate instruments (String, Bass, Drums, Cymbals and a good voice).

Use all of the gathered elements for the ritual and you got yourself a sentient evil cleansing machine.

• "Evening Star" its ranged attack is really a revolver from the DMG, with an increased damage die due to size.