Rudimentary versions of all of these will be available in the initial release, except upgrading your tower. That’s a bigger project that will need some time dedicated to it that I just wasn’t able to get to yet. Some of these things are intended to be discovered through play so I may stay a little vague on them.
You can upgrade and learn new spells by studying magic tomes, spell books, and other magical items you find out in the world. There are other methods of gaining power you might come across that are more quick or powerful, but at the cost of gaining various types of corruption. There are a few types of corruption, which all have both positive and negative effects.
One of the factions you can trade with is The Most Ancient and Sublime Grand Feline Order, who barter in secrets and knowledge. You can trade secrets of magic with them for other types of secrets and knowledge, such as them revealing the layout of a location you visit.
It’s possible to gain a following of cultists that will follow you on your adventures. In addition to fighting for you, their worship will enhance the power of your spells.
Brewing potions and crafting magic items are fairly straightforward, though one difference from traditional game crafting is that rather than have a set list of ingredients for each item, you can use any item with a given set of properties. For example, to make a potion of fire resistance, you can use fire herbs, dragon scales, or other fire-aligned items you might come across.