I was looking to clarify how levels of a prestige class work for spells per level and the bonus spell that a thassilonian wizard has for his specilized school.
The bonus spell reads as follows:
"A Sin mage receives two additional spell slots of each spell level he can cast. These bonus spell slots must both be used to prepare the same spell from the wizard's school of specialization, allowing the wizard to cast that spell twice (as he has prepared the spell twice). The wizard cannot use these slots to prepare two different spells, even if they are of the school he is specialized in."
The way I read this is that a level 5 sin wizard with 2 levels of lets say bloatmage gains 2 bonus slots for his level 4 spells because the prestige class increases his effective wizard level to 7.
Is this the correct interpretation?
Yep. As long as you can cast 4th-level spells, you get the extra 4th-level slots, same as a "regular" specialist gets one extra 4th-level slot.
Same conclusion, different path: Sin Magic is an ability, gained at first level, that sutomatically scales to the highelst level of spells you can cast. Domain spells work the same way.