Solution: Tower of Justice ( Hades' ) HEAVY LAGS!
Ok we all know obviously that it's all Hades' fault and part of his plot to triuph and take over the world.. Yes! It is HADES who causes your ( Hero ) PC to lag, to stop you from saving the world ( again ). Heck it's Hades' main power and ability that he uses against the Hero is to make his perception of reality faulty... causing, what we call simply: LAG. Okay well I have one solution that might help you combat his strong psychic powers and render his strong ability less powerful.
Okay jokes aside, Here're the instructions:
In your Documents/My Games/Titan Quest - Immortal Throne/settings folder there is a file called "options.txt" open it.
Scroll down and find a line
forceSingleProcessorMode = false <--- Make sure it's false! If it says true, change it to false. This should decrease Lags by a Large margin if you have a multi-core processor.
Hope it helps! If it does would be neat to get it a stickie. Also some people that actually found this of help could actually post here and say so, would also encourage and prove to others that it works.