Spell Thesis
Source
The Threefold Conspiracy: Puppets Without Strings pg. 50
You have researched a single spell in great detail. Select a single spell you know. When you cast this spell, its DC is increased by 1 and you have a +1 bonus to caster level checks to overcome a creature’s spell resistance. In addition, once per day, you can cast this spell without expending a spell slot. Each time you gain the ability to cast a higher level of spells, you can swap out the spell associated with this ability for a new spell that you know.
Dragonscript
ID
d9b5be2ca1192931beb1efb4