The Vetruvian Imperial Guard dispatched to hunt down the rogue mercenaries said to be terrorizing the villages near the city of Tyvia were settling down for the night when one of their scouts, a wind striker to be exact, came bearing news of a small group of heavily injured primus fists. The commander of the camp, Captain Oberon of the house of burning sands, demanded that they be brought to him for interrrogation immediately.
Upon seeing the normally proud primus fists reduced to the pitiful, terrified stragglers before him, Oberon knew something was wrong. After a quick, but nonetheless foreboding, interrogation Oberon gathered his men and set out to reach these so-called Ruins.
After two days of continuos riding, Oberon and his men finally reached the dreaded ruins. He rallied his men, setting 15 imperial mechanysts to begin creating several fireblaze and windstorm obelisks for the upcoming battle. Bearing his trusty wildfire ankh and the staff of y'kir entrusted to him by his father, he brought the men not assigned to the building of the obelisks into the Ruins.
Upon his entrance into the courtyard Oberon frowned as he came across the decaying remains of the mercenary group he was hunting. Despite being hateful bandits, Oberon said a quick prayer to Eyos and continued further into the ruins, albeit with a more cautious eye. Delving into the labyrinth underneath the Ruins, Oberon and his men came upon something he had never expected to see, an egg. Crackling with green energy and almost as large as his own head, Oberon instantly knew what egg this was, " One of the Thirteen," he said with awe. Seeing the large mound of goop it lie next to and what could've passed as shredded cheese all around, he only had an instant of warning before he and his men were swarmed! Countless demons and parasites crawled out of the cracks in the walls with the hulking silhouettes of horrors close behind. The pyromancers immediately went into action, blasting away most of the smaller swarm before they got too close. The iron dervishes, their metallic bodies shining with the power gained from the constructed Obelisks outside the ruins, formed the first line of defense against the horde. The platoon of Flacius' stood behind them, chanting wards of power and protection for Oberon while summoning ethereal blades from their arms. The Dunecasters stood in the back with the pyromancers, chanting spells of strength to boost the dervish even more, while the group of Aymara Healers stood beside Oberon, prepared to mend the wounded. As the two forces clashed, Oberon commanded a few of the Dunecasters to prepare a Circle of Dessication in preparation of their retreat. Oberon himself stood in the middle, blasting enemies left and right and as the horrors approached, he surged forward felling one with each burst of his ankh. As his ankh's power dwindled and his forces grew weary of the fight, he spotted the signs of another wave of horrors fast approaching! With the authority befitting that of an Imperial Guard, he commanded his forces to fall back, the wind strikers helping some of the wounded while the pyromancers provided covering fire for his forces. It was only after reaching the first level did he hear the telltale BOOM of the Circle of Dessication going off, killing what was left of the horde within the ruins. After a quick skirmish with a few of the forces chasing him and his men down, Oberon was able to Dominate the Wills of a few of the pursuing horrors, learning of what had happened here as well as the whereabouts of a couple of silhouette tracers from the original mercenary group. Having stationed a few of his men to defend the entrance to the catacombs below, Oberon quickly rendezvoused with the surviving silhouette tracers who informed him of the single, remaining egg clutch.
Oberon was apprehensive of the information, but quickly became ecstatic at the briefing that the room itself lacked a ceiling due to the discrepancy of the Ruins. He thanked Eyos as it was still dark and, after leaving his equipment with a team of Mechanysts, Oberon, accompanied by the two silhouette tracers, traveled to the last remaining egg clutch, situated at the uppermost level of the Ruins. Facing the Giant mass of the clutch and the few horrors guarding it, Oberon made a sign, invoking a powerful spell one that would call upon the fury of the stars to destroy the foes before him! One by one, ethereal avatars of the Stars came crashing down, smiting the horrors and the last of the egg clutches!
By the time the sun had risen, Oberon and his forces had cleared out what remained of the demonic menace infesting the ruins, and by burning the bodies had ensured the prevention of the resurrection of the demonic host. After wrapping up the Egg he found in the Labyrinth, he gave it to one of the Wind Strikers before dispatching it back to Kaero with a report of what had happened here.
He then ordered his forces together and, assembling a one use fountain of youth, healed them up to full. He then prepared to fortify the Ruins, awaiting reinforces from either Tyvia or the Petra Fortress to relieve him and his men.
Remaining forces (Vetruvian):
- Oberon with full Staff of Y'kir and Wildfire Ankh
- 10 Aymara Healers
- 19 Imperial Mechanysts (one blew up in a mechanical accident)
- 30 Iron dervishes (25 are given +2/+2)
- 23 Dunecasters
- 15 Falcuis
- 12 Pyromancers
- 2 Silhouette Tracers
- 1 Horror full health, 1 Horror 2 health
- 3 Fireblaze Obelisks & 2 Windstorm Obelisks
At this point, only the uppermost of the ruins are cleared of horrors (and corpses). This is a separate group than the original sandshield mentioned in the OG post. The reason why they seem so powerful are that they are Imperial Guards, therefore starting off with a +1/+2 buff (I equate that to their training). They also haven't met up with the golems mentioned by @jon678910 since the golems are at the first seal which is at the bottom of the Ruins.
Vaath the Immortal is one of the Thirteen Aspects who are, if you believe the Codex, are essentially immortal as they can be reborn as an egg. Oberon doesn't have his egg shattered because A.) it's hard AF and B.) If he killed him, it could spark a war between the Imperium and the Thirteen Aspects, which is not his decision to make (He's a commander of a unit in the military, not one of the ruling houses!)