The One above All (House Rule)
The countless gods of the multiverse in their many pantheons, in all of their hallowed, glorious, wise, loving, foolish, spiteful, cruel, and unimaginable ways are all merely facets of an infinite greater god. This foundation of divine entities is known to only a few powerful gods of secrets and knowledge and even they have difficulty believing it to be true.
What this means for players
This is mostly a background note and doesn't change the ways divinely granted powers like that of clerics function. The PHB stands. I use this "Infinite Deity" rule to open up creative opportunities for characters that must take up the somewhat servile mantle as a worshiper of a god as with clerics, or serve under the patronage of a god or greater being such as with Warlocks. All PHB gods/patrons are available without question as long as it fits your character. Any supplemental WotC published gods/patrons like those in Sword Coast Adventurers Guide are fine as well. Just make sure I have a heads up so I’m not surprised. Beyond that, WotC Unearthed Arcana and third party supplemental works are generally accepted but again make sure I have a heads up and approve.
The real power behind this house rule is the ability to create and greater entity from scratch. The gods are infinite and not all are known, even to those who max out their Religion/Arcana. Wanna worship a completely new deity of your own design? Let’s give it a go! In general just have some good mechanical or RP reasoning for your home brew god and some fun and interesting details for them and if I give the thumbs up we can work it out nitty gritty from there.
On top of the PHB and published works baseline, there are a few House Gods for this world. Among the house gods there are listed a few gods with the Living God descriptor. These beings all generally have a level of power on par with Lesser Gods but are bound in some way wo a specific local outside of which they are rendered impotent.