@MacBalance @cstross "When I cast this spell, I discovered that Belphegor is no longer Lord of Eternal Pain, and that I now need to call on Astaroth for that. But the invocation for Astaroth seems to be totally different. Can I still use these black candles, or do I have to throw them away and lay in a stock of hemlock?"
"When I summoned Belphegor I wanted a loud shouty demon, not a 1970s Polish jet-propelled biplane cropduster, dammit!"
"Not my fault, guv, it's just a namespace collision!"
@cstross @darkling @MacBalance see also refactoring an old spell base after a rebranding and having missed some strings that need both updating and localization.
Also merging branches requires cycles so multidimensional incursions with the accompanying bit rot poisons the whole history (see multidimensional) and may or may not be recoverable.
A kind of Heisenberg paradox if you will - observed or otherwise the spell is dead and is probably going to make you wish you were too.