This is Ignisimbre, a spookpup. The thought I have for them is that they were cursed by the talisman they wear, but because they're willing, the curse can be lifted until nightfall, where it regains full power once more. Those that see them at night would likely see the embers of fire flitting over their coat, and the red and gold, glowing skull and necklace from a distance.

This is a Spookpup that I was gifted with from ♥ Thank you!