Quote Originally Posted by DracoDei View Post
When does it gain mental ability scores?
I don't see any reason for it to have them, how about an advanced version of mindless?

Greater Mindlessness (Ex): When phage has no intelligence it has immunity to all mind-affecting effects (charms, compulsions, phantasms, patterns, and morale effects), when it has no charisma score it's immune to all hearing and language-based effects, when it has no wisdom it's immune to all sensory-based effects.

Otherwise, the source needs to improve his own mental scores to give it sentience.