It is part of canonical Sims lore that following the Century Conflict between Spellcasters and Vampires, the attempt of the Spellcasters to cast a spell which would instantly cure all vampires from vampirism backfired, giving Lake Lunvik its powers, but also causing a massive overload that ripped the Magic Realm apart, causing it to exist in fragmented pieces separate from the 'real world' as it does today.

For storytelling purposes, it would be awesome to have a spell that a very powerful mage can perform to 'defragment' the Magic Realm, allowing it to exist alongside Glimmerbrook, as well as adding moodlets, conversation interactions, and gameplay interactions relating to this. You could have the mage gain a special trait, or even add a new Aspiration with goals that culminate in defragmenting the Magic Realm, like the Strangerville aspiration.

Generally, requesting for content to be made for you is frowned upon on this site. See the rules for more info: