Vampire loreCHADs I beseech thee! Come to mine aid, and thou shalt hath thine (You)!

I already know the basics and am seeking more. Give me the deep dive on Obtenebration, the Abyss and the Abyss mystics, and Lasombra lore as a whole. What exactly is the abyss, what is the nature of obtenebration, and is there a greater entity at work in the shadows like how Vicissitude is tied to an eldritch abomination and has utterly screwed the clan? Is the Abyss canonically connected to an opposing force to creation and life, is it Hades or Hell, or is it something else entirely? How does the Lasombra interact with Wraith canon and are the two lores compatible? Traditionally, the Lasombra were Sabbat, but what lore is there for the Lasombra who sided with the Camarilla? Antitribu? Also, how badly did V5 screw the lore?

I'm most familiar with V20, so recommend or explain any differences with earlier lore, if you'd like. Gimme whatcha got.