This link describing the magic system is here.
A summary of the high points:
- Basic magic is cast using a 'spell check' of 1d20+caster level+spellcasting stat
- 1 is a critical failure, a 2-11ish causes you to lose the spell, and increasingly high values increase the power of the spell.
- You can 'spellburn' and sacrifice both in and out of game resources (physical stats along with role playing bargains) to increase the power of spells.
- You may sacrifice a spellslot to gain the ability to call upon a patron.
- Spells are mercurial, meaning your character interacts with every spell uniquely due to their heritage or the stars.
It's a good read, I suggest checking it out.