This is for an AU I've had in mind known as "The Storm War". An alternate season 9 arc involving the last of the unreformed villains invading the Equestria Girls human world rather than Equestria directly, forming an axis alliance known as the "Pact of Thunder", consisting of The New Storm Empire, the newly established Umbrum empire under King Sombra, New Tambelon, ruled over by the revived Grogar (the actual one) and a re-established Changeling Realm founded by Queen Chrysalis and a faction of Changelings that remained Loyal to their Queen and weren't changed by King Thorax.

The one who rules over this revived Storm Empire is an usurper who had taken the throne after the defeat of the original Storm King. A Neo Storm King so to speak. In order to compensate for the loss of the Staff of Sacanas he has embraced scientific and technological advancement. Mechanizing and reorganizing their army to wage a new kind of warfare unlike any that had been fought in the history of Equus: Modern Warfare. Making this empire one of the few powers on Equus to have undergone industrialization. As a result, the other member's forces also underwent industrialization and mechanization as well. Albeit unwillingly at first.

The members of this pact did not sign this willingly, though as they were forced into doing so with a boom-stick(gun) aimed at their heads.

Tirek is not officially a member but is under heavy control by the Storm Empire. having been mentally reconditioned and fitted out with a series of suppressors and dampeners to prevent him from draining the pact's magic as well as preventing the pact from losing control of him after absorbing a certain amount of magic. Less a member and more like a living weapon.

Cozy Glow was simply left to rot in Tartarus due to being rightly seen as an insignificant and pathetic brat in the eyes of the Neo Storm King.

However, this pact is still prone to infighting despite the efforts of the Neo Storm King to keep the other members in line. All the members secretly plan to betray one another at a certain point in time as sharing power does not fit in with their line of thinking and in Grogar's case, the Neo Storm King would sometimes get into heated arguments with him over what kind of warfare was the best. Wether Monsters or Machines are the best way to fight.

All of their reasons for Conquering the Human world is simple. A new Domain beyond the prying eyes of Equestria that has more resources they could use to eventually defeat Equestria in the long term as invading it immediately and in the short term has become a suicidal gambit as the kingdom had become arguably the most powerful nation on the planet thanks to having so many allies and the (literal) power of friendship and harmony. The Human world has no magic as well as the fact that they are divided and bickering with one another would just make the conquest even easier.

The human world would have all the resources needed to build each villain's forces to an overwhelming scale. The Neo storm king would have more raw materials to feed their war machine, Sombra would have plenty of Humans to expand his mind-controlled army, Chrysalis would have plenty of space to build more hives and rebuild her kingdom and Grogar would have more than adequate grounds to test his monster experiments.