Might be interesting for historical aspects, but I’m not really a history mare.

I’d like to read some about magic from their age. I’ve heard they had access to magics that fell out of favor centuries ago, or were outlawed for one reason or another.

See, earth ponies historically shunned magic. Crystal ponies didn’t. They found ways to access it through enchantments and magically-infused objects, of their own design, without unicorn aid. Largely antiquated compared to what unicorns can do today, but incredible for it’s time.

With the crystal ponies return and modern day practices, it’s possible we may see a resurgence and expansion of those ancient techniques. Depending on how integration and regulation pans out, we may be on the cusp of the next magical age.