It appeared in Swamp Thing in i think in 1986, right after the Crisis. It is the only being that is equal to God/The Presence in the DCU. In Vertigo Sandman Lucifer has talked about the Shadow Creature aka TGEB and when it tried to destroy everything. I have heard it appeared again later on in DC The Spectre comic and went back up to DC Heaven and talked with The Presence and then they both joined together, don't know if thats true or not.