I was trying to decide how to title this thread in a way that worked, and thus this came about. It isn't perfect, but I'm trying to be honest.
Last week I published a book, and I've been working on a few pieces of Pathfinder content to approximate some of the story elements.
Elementalist Warrior: This is a fighter archetype that I would view as most similar to the Synthesist Summoner. The fighter forms a contract with the spirit of an outsider which they can summon into their body or gear to boost their abilities. At the moment I've only created the 4 classic elemental spirits for this, but in many ways its designed to make them less magic-item dependent.
Dark Invoker: This prestige class was quite honestly inspired by the massive debate over spells with the Evil descriptor, and me wondering why a prestige class or the like didn't use the classic of 'how power corrupts' as a theme. This class sells their soul to a dark power and gains the ability to add dark invocations to their spells to make them more powerful. These invocations are limited to those spells that have the Evil Descriptor, but the dark invoker can add the descriptor to a number of spells they know. These invocations may also be used to summon fiends, giving increased flexibility.
Sorry about using an outside link for this, just wanting to keep closer control over the text.
If people want to give me feedback, I'd appreciate it, as I work on further content for my world. Unfortunately, trying to actually make everything work right would necessitate adjusting the entire system to a spell-point system...and I don't have time for that. Yet.