[TOMT] [BOOKS] [FANTASY] [2000s-2020s?]
I remember a particular fantasy series in a fairly generic high-fantasy setting, but with very identifiably strange magic. "Wizards" were those who cast directly from their own life force, and so effectively burnt up their lifespan with every spell. "Sorcerers" were still trained in magic the same way, but had 1 or more Elementals who regenerated magic naturally and so could safely cast as much as they like. Lesser elementals only regenerated magic very slowly though, and the greater ones who could draw it in faster were rare.
The main character was taught by an old man who somewhat predictably turned out to be a truly ancient wizard, from back when they weren't the shittier, cheaper version. This was done by compressing their life force, up to 3 times for 1/8th the size, and allowing the ambient magic to filter in and take it's place. This could then be used to cast safely, and coincidentally massively extended their lifespan
Other details include: Very old school vicious fae, they even turned the old mentor into a talking ring after he died for the lulz and also possibly old romance, there was a princess love plot, the king was evil and also maybe turning people into elementals I think? The main character gave birth to trolls at some point, no idea how but I remember the jokes about it. I'm not entirely sure on the older bound of the dating, but I remember was still getting published when I read it around 2022, so I erred on the side of caution.
Thank you in advance, all!