Source: Ultimate Spheres of Power
Casting
A sphere investigator may combine spheres and talents to create magical effects. A sphere investigator is considered a Mid-Caster. (Note: All casters gain 2 bonus talents and a casting tradition the first time they gain the casting class feature.)
Limited Alchemy
A sphere investigator is not able to create extracts, but retains the other uses of the alchemy ability.
This alters alchemy.
Spell Pool
A sphere investigator gains a small reservoir of energy he can call on to create truly wondrous effects, called a spell pool. This pool contains a number of spell points equal to his level + his casting ability modifier (minimum 1).
Magic Talents
A sphere investigator gains 3/4ths of a magic talent every level (the same progression as he gains caster levels).