History
When Vulcan was reprogrammed by the Progenitors, he was left with a thin shell of normality that hid the chaos underneath. Returning to Earth and being accepted into the Summers Family, Vulcan subconsciously created energy constructs of his deceased friends Sway and Petra, who at the time could not be resurrected by the Five. Vulcan believed the constructs to be the real Petra and Sway refused to even contemplate otherwise, and spent most of his time getting drunk with them. Believing this was his mind's way of slowly healing, his family indulged his fantasies.[1]
The two constructs appeared to be influenced by his hidden self and not outmost shell, as they possessed a degree of autonomy and kept calling Gabriel "Emperor" despite him not wanting that.[2] Xavier even allowed Petra to teach a class to the young students,[1] and both "Petra" and "Sway" accompanied Vulcan to Otherworld where they battled against the Swordbearers of Arakko, the first Horsemen of Apocalypse, the forces of Arakko, the Amenthian Daemons, and the Summoners.[3]
Eventually thanks to the actions of Wanda Maximoff the resurrection of real Sway and Petra became possible, but Xavier's attempted to breach that subject with Vulcan resulted in a violent confrontation.[1] What became of constructs following Vulcan's death and resurrection by the Five has not been revealed.