please see attached issue at: https://gitlab.com/modding-legacy/blue-skies/-/issues/175

I'm not sure what you're stating here -- the adventure file had a boss statement for both skies dimensions as the other dimensions did (which worked fine), in this case the blue skies folks block such spawns. It seems like you forgot to check for a null instantiation before assuming the object would in fact be non-null.

Apotheosis does not ship a spawn rule for any dimension other than the overworld, nether, end, and twilight forest. Any other modifications are done by the user (or pack developer), and it is their responsibility to provide adequate boss jsons.

This is the result of user error, you cannot configure bosses to spawn for a dimension without providing any bosses for that dimension.

No, boss json files must be provided by a datapack
https://github.com/Shadows-of-Fire/Apotheosis/tree/1.19/src/main/resources/data/apotheosis/bosses

Alright ,and if they mimic the existing spawn lines exactly, shouldn't they be expected to function just like the others? And if they don't function just like the others, whose responsibility is that?

Thank you, i'll take a look.