All of it has fallen through, all the planning, all because of his damn brother, Scorpan had ruined it all by warning the Rulers of Equestria and now Tirek was forced to rot in Tartarus for all of eternity, all because his brother. "Damn you Scorpan!" Tirek yelled into the darkness, there was nothing he could do now, Cerberus would prevent any escapes and even if he could escape then Celestia and Luna would probably just turn him to stone like they had Discord.
"Damn you, when I get out of here, I'll drain the life essence from you and all your little ponies!" he shouted, reared up and shattering the ground when he came back down, he still retained his monstrous from, but slowly it would leech away til he became sickly and weak, as was the curse of Tartarus, you never need nourishment, but you'll still grow weak from hunger. Tirek continued his fit, free to move around for he wasn't trapped in a cage for only the worst criminals earn those, so he yelled, charged, reared up and smashed the ground multiple times.
"Would you keep it down!" yelled a voice from the darkness, breaking Tirek from his anger towards the ponies momentarily and diverting his anger towards the unknown speaker "Who dare command The Great and Powerful Tirek?" he bellowed into the darkness. Wind began to tear through the cavern, striking Tirek with an icy sting, though he felt the wind, it didn't push him down or force him back, from the darkness came three spectral beings hovering forth, the front half of their bodies were equine while the back shifted and swirled like the wind "We did" they said in unison in voices that sounded like the gusting wind "And you would be wise to listen to our words for We rule Tartarus and you are now one of ours."
Tirek smiled at them, baring his fangs "Oh really" he said, sarcasm palpable "And who might it be who I am serving?" he crossed his arms over his chest and standing up straight, smug. They hovered forth and glared menacingly at him "We are The Windigos, The first threat to Equestria and the most dangerous force in Tartatus" they said, hovered apart and swirling around him "Serve us or have Tartarus as your grave."
Tirek laughed at the Windigos, not shaken by their threats "I am Lord Tirek of The Southern Dunes, Son of Lycon the Feared and Shaynera the Nightmare, what makes you think you could force me into servitude, as a matter of fact, whats to stop me from taking over this pit?" he said, his voice echoing through the caves of Tartatus with force "You are but gnats to me". The Windigos laughed, a sharp keening sound, causing Tirek to grow and "We fear nothing" they said, speeding up as they swirled around him, Tirek could feel what they were doing, they were creating a vacuum "We are the Lords of Tartarus and Kings of The North, you could never stand against us"
The Windigos broke from the cyclone and lunged at Tirek, something he hadn't expected, one sunk it's teeth into his shoulder, dangerously close to his throat, the other to bit into his forelegs, causing him to cry out and stumble forward in shock and pain. He growled and grabbed the first Windigo and tore it from his shoulder, black ichor seeing fom the wound, he slammed it down on its siblings causing them to release him, they easily floated back up and continued the attack, this time headbutting his chest together, knocking the air from his lungs and pushing him back.
Tirek didn't recover fast enough and before he knew it, they had latched back onto him, this time two were biting into his forearms and the third sinking its teeth in his side, he roared in pain and panic, he reacted naturally, shooting a magic beam at the third and causing it to release his side, falling to the floor, unconscious. He brought his arms together and slammed the two Windigo's heads together, causing them to let go and fall to the floor in a daze. He pinned them down and barred his teeth "Who rules who now?" he growled to the two, their eyes fearful.
"Our children" said the third, pushing itself up with it's hooves "Will rule Equestria, at long last brothers, we have found one who who can bear our young and conquer Equestria" it said, without it's siblings, the voice had lost its ethereal quality, sounding quite ordinary now. "Lord Tirek of The Southern Dunes, We would be honored if you would bear our young" the three spoke in unison once more, the third bowed its head while the other two, still pinned on their backs and unable to move, simply shut their eyes and lowered their heads to Tirek.
He released the two from his grip, confusion clear on his face, the two Windigos hovered up and helped their sibling back into the air, once they were all back up, they hovered before Tirek "Well, what do you say?" they asked. Tirek shook his head and laughed "Is this some sort of joke, firstly, I am a male of my kind, I can bear no young and secondly, why would I want to, you attacked me and now you ask me to have your children for no reason" he said, laughing. The Windigos however did not laugh, instead they began to circle again, slower though and much less threateningly "Oh, but you do not understand" they said "For our kind, gender does not exist and we can breed with whom or whatever we want, though we can not breed with our own kind and besides, you and us have a common goal, revenge on Equestria, all of us were locked here by Equestrians, but they have never thought of us breeding and creating children stronger then ourselves."
The halted their swirling and turned to Tirek "Bear our children, Lord Tirek, and take your revenge against Equestria alongside them and us" the said, moving down to him and bringing themselves close to his body, running themselves along him and sending his body to bliss "Yes, yes, this plan is good" he said, his eyes closed and smiling "Yes, I will bear your children, to take my vengence"
And with those words, the Windigos carried him into the darkness to begin their joining of dark lineages and evil bodies to create powerful monsters, but little could anyone suspect that those monster would be as weak as they come, but that is for later, that is for when the story really gets going.