In two Equestrias, Dr. Thaddeus Alxion is renowned in fear. He is the one who imprisoned the Solar Twins and left the Lunar Twins badly injured, he was locked away, deep inside Tartarus, never to escape. In fact, Cerberus himself guarded his cell and one other. Now, his fellow prisoner has escaped. Unbeknownst to the rulers, Thaddeus was far from evil, and has chosen to end Tirek, and with the blessings of Tartar itself, he has left to end it all.
One problem, his daughter is now in Equestria.