My assassin has a base INT of 12, but he can cast (and I tested) spells of 3rd and 4th level. I do not have any INT boosting items equipped.
Just thought I would report it since it's listed in the Custom Changes thread:
Apologies if this is previously reported.Spells require a base Intelligence score of 10+spell level to be cast. Intelligence boosting items will not provide bonus spells for the Assassin