Void Reactor

Voidtech reactor, that can be found only in the Void (from which you also have to gather fuel to it). In fact, noone has even a slightest idea how exactly they work, since they are a complete and utter mystery. Exactly as their fuel, known as Void's Tears, a semisolid material that in low temperature congeal into form similar to tear.
Void Reactors produce much more energy that Singularity and Hyperspace Reactors, without having a single noticable disadvantage - rather than decreasing mental state they actually tend to cause longterm improvements, sometimes being actually used to treat hyperspace schizophrenia, and after being destroyed they do not explode, and neither does their fuel. Well, not a single disadvantage apart from the fact that their fuel still has to be gained from the Void, which means the supply is very limited and they have practically no usage in regular military.