My question relates to the memory aspect. Say I learn a Level Five spell at Level 10. This takes 5 circuits. Say I later replace that spell with a new one used on me, this time a level 4 spell. Can I later decide to replace that level four spell with my old level 5 spell? Or do I have to be exposed to it again to bring it back to memory?

Essentially, what I'm asking is if memorized spells are in a mental spell book and can be relearned at any time if the required number of circuits are available. Or is it a "shredder system" where once a spell is forgotten, it is gone and can't be retrieved?