While technically alive, magnagogs have little in the way of personality and are driven via telepathic command.
The Sogans were a mystically aware technological society. Queen Stavarang is the last surviving Sogan in the galaxy
Potentially the most powerful summon created, the Final Judge of Man and Earth
Rather than making a baddy impossible to hit, consider giving it mega-hit points.
Super hard to hit leads to great player frustration. Allowing them to do damage leads to a sense of accomplishment. another variation of this would be to give the bad guy a forcefield that shows damage.You could also give them a mastermind ability that sluffs the damage of to minions who should be easy to kill.Once in a while a super high to hit encounter is ok ,but it should be few and far between.
Your mileage may vary