Why the door matters and Planar feasting

This book is a rough diary that is basic in design and in it's draft form as though part of an academic article that did not make it to the publishing stage. It is the only book of it's kind and so exceptionally rare... it is around 500 years old and is wrapped in tight abjuration magic to protect it from the elements and outside forces, implying someone took a long time to ensure this book was protected and would be preserved against the test of time.
A key excerpt from the book: That door, locked, sealed and only corporeal under the light of the sun and moon in tandem. Can only be opened with the channeled energy of the old gods... not the newly forged replacements that govern whilst the creators wait. 
The world wept when the door closed and we watched our lands ripped away; we will forever miss the other countries... despite knowing that they are safe beyond the door. Most of all though, the clerics weep for their missed powers and feelings of the world that they can enjoy. However, that is not the end for us. 
Thanks to the work of the Scribe's school, there is still a method of siphoning power from that door and the latent planar energy of the world. This is known as planar feasting and involves the coaxing of planar energy through a blood offering, when the offering is complete and the planar energy emerges from the door it will be frigid and cold and that is the opportunity to feast, to feast you must....
From here, the pages are ripped out as though someone chose to destroy the knowledge within.

Type

Journal, Medical