dave2008
Legend
In the BECMI Immortal rules, gods (Immortals) couldn't enter the Prime in their godly form, they had to assume a mortal form. Page 3 of the Player's Guide to Immortals: "Whenever the character revisits the Prime Plane, the character can only assume his or her original mortal form." There is more description on page 25 under Original Form.So, you haven't got a quote, and have in fact made it up? It's fine for it to be the rules for your campaign, but please don't claim it's official D&D lore.
That Planescape quote says absolutely nothing to support what you were claiming, which was:
And that's simply not true. There is no D&D lore I'm aware of that supports this notion that "every other god" will come after you for messing with the Prime Material. There's no trans-pantheon agreement not to mess with the Prime Material. It might be a bad idea in the sense that you're pooping where you eat and you're going to piss other gods off if you cause a huge mess and kill their worshippers, but that's a completely different thing from "under pain of death by every other god coming after you".
Also, in the 2e Legends and Lore page 6: "They never visit the Prime Material Plane in their true forms, for this plane is the focus of so much divine attention that it is impossible for any deity, no matter how powerful, to enter it personally." And on the same page under Avatars: "When a god has business upon the true Prime Material Plane, he must send an avatar.
From the 3e Deities and Demigods, page 18, intercession by the D&D Pantheon side bar: "The gods of the D&D pantheon are keenly interested in events on the Material Plane, but they stay on the Outer Planes by general agreement..." and "...When the deities of the D&D pantheon intercede in mortal affairs, they often do so indirectly or through intermediaries."
I am sure there is more like this, but these seemed like the most broadly applicable that I could think of off the top of my head. So I don't know about tracking down another gods, but there is a lot of lore about gods not being able to directly act in the Prime. Fortunately I don't use published settings so I am free to ignore all of that and have gods walk among mortals in their full power (if I want).