The hyperborean realm of the Eternal Flame
Clarence was singing in harmony as his kind is wont to do. Their singing reinforced the "song of existance". It was a somewhat important job, even though only a handful were needed rather than the hundreds that did so. He and others near him noticed the pin prick discordence in the weave of melody that was the material realm. Those dark alien notes rose up. The Angel Mind touch the Divine and followed the new sub melody. Humans would call it a plan. Angels dove to the material realm and, of course, if any world was going to be causing problems, it had to be Earth. Oh well, at least Clarence would know his way around.
The PCs find a small green glass bottle, something can be seen writhing within the smoked glass. If the PCs open the bottle a repulsing form of life will pour forth and grow in size. A genderless beings of soft pliable purple flesh towers before the PCs, it has no detail, no distinguishing characteristics except for a narrow slit for a mouth that holds rows of inwardly curving teeth.