Spellplague lore questions
I'm working on a character concept that I like the backstory of and I may turn into either the main character I play as or as a backup if I'm ever in a campaign. I want their backstory to be as compatable with the lore as possible but part of it involves encountering a creature with an ability that had a major change between 3e and 5e; from what I understand a lot of the major changes between 3e and 5e was due to the spellplague (or more accurately the changes between 3e and 4e but obviously extending to 5e). However the lore about it seems a bit dense so I have a couple major questions about it:
- Did it just change how magic/spells work or did it apply to other things as well? Would creature abilities that aren't directly associated with magic have been changed from it?
- Were there exceptions to it and if so what prompted those exceptions? Geography? Species? And if there were individuals who still retained one or more features they possessed before it could those features be passed down and/or recessive?