There is one thing that is definitely related and another that may be.
If you go into the details of "Dreadful Awakening", it has a small bit that says this:
PlayAppearance: DependentOnCallingEffect=>1, AppearanceSpec=>epp.qtr.1x4.raid.asation.trash.cav e.secret.dreadful_entity_grow
This once again says that the Dreadful Entity is in the Asation "Trash Cave", but it also says that the entity "grows".
This might have to do with the red and blue plants in the cave, but it appears to only be an animation.
This item might be what causes activates the dreadful awakening.
Or maybe not. Just something that I didn't see get mentioned.