[The_Outsider]

Yeah, they do sound cool, but AFAIK they are purely fluff, there a no rules for them in any Imperial Armour.

I believe they are titans whose 'pilots' are psykers, they use systems to enchance their psychic strength (much like a psychic hood except on a far larger scale). They are very rare and are only used in the most dire cases (even when compared to other tians).

Shame really, imagine a titan using storm of the emporer's wrath, except on an ordanance scale!

I may be wrong but thats as much as I know.

 

[The_Outsider]

I think (though don't hold me to this) the Divisio Telepathica are a part of the adeptus mechanicus that specialises in psychic weaponry and the like, these guy are probably responsable for making the nemesis force weapons.