No, Im just curious if there was a side quest for a 2nd crystal ball as I already finished the story and Rachel (and only Rachel) was banished
There is only the one crystal ball and you can only save Rachel prior to the ending. If you’re curious how to get it, there’s a page on the wiki that covers most major decisions and details their effects and the endings you can end up getting. For stuff specifically about how to get the crystal ball, see here. Warning for massive spoilers, potentially even if you finished the game.
More info on the specific conditions to get the crystal ball: https://outsiderartisan.miraheze.org/wiki/Secret_Storyline:_The_True_Power_of_Alchemy