This supporting image is unique because it shows 2 beasts mouths together creating an entrance into the depths of Hell. The mouths of Hell are packed full of unworthy people and are being locked out by an angel with a key to the gates. This image is called Hellmouth, locked by an archangel, from the Winchester Psalter of about 1150.
Image Credit: https://en.m.wikipedia.org/wiki/Hellmouth#/media/FileEin_Engel_versperrt_ die_Pforten_der_Unterwelt_mit_einem_Schlüsel.jpg
Reuse License: Public Domain