Let's try and do some digging, yeah?
Little was known about the Opalescent Tower, save that it had been erected by the Royal House of Mirel about twenty centuries ago, and had been the subject of much magical experimentation under prior Kings.
We know little about the Towers, save that they can probably be experimented on?
At last they reached the border of Augustine's inner dominion, the simple command tent now elevated atop a foreboding pillar, column of earth upthrust from the swamp around and fissured with seams of azure and gold. The Cloak of Sky writhed and snapped, bristling before the form of its nemesis: stone to its air, depth to its void.
The senses swam before that impossible tower, its fell radiance swarming mind and spirit. Augustine's forces dwelt in the corners of the real, their might sufficient to rend soul and sanity; yet he was the envoy of a greater power still, before which even such terrors as this were less than motes in the breeze. He flared the Ring of Crimson, bright burning Blood which brought mere Passion to heel, and even fear itself could naught but yield before its fury.
The Cloak of Sky happens to dislike the Tower of Earth. We don't know if this means it would be more willing to eat it, or less. We also know that the Patron this tower represents is of a lower power-tier than Claumngor (who is apparently made up, anyway). What this indicates is that Augustine probably used her magic to tap into the primordial counterpart of the Sky (the Earth) and fashioned it into a deity-spirit for her to use. I suspect that this is a monument to Claumngor, in the same way that the Opalescent Tower was probably a monument to Arulothel.
They reached the foot of one enormous Temple, a trapezoidal slab of dusky stone rising mountainously above the bustling mundanity surrounding. Filthy smoke belched in endless torrents from serried rows of precisely-cut rectangular windows. The building facade was half in the midst of construction, old-fashioned murals and colorful glaze being steadily tiled over by steel-wrought iconography in sepulchral hue. Gray-robed magi manned the scaffolds, examining the newly-imparted cladding, summoning potent divinations with brusque, artless gestures.
A quote from an earlier update fills in some of the details of the themes of this Claumngor. Yes, Earth, but also iron. Industry, smoke, steel, sepulchre. Even the system itself reeks of industrialization, homogenous and uniform but lacking life. Honestly, this entire arc seems to heavily concern itself with Age of Wonder/Heroes -> Age of Steel/Machine, where hero-units are felled by the grinding efficiency of millions aligned for a single purpose. Similar concepts are found when Seram shacks up with the Joanians and Yong Liefang's Dao.
"Outsiders, are you? We don't get many who can afford to tour our city these days. Yes, this used to be a Hall of Arulothel, the Patron Spirit of House Mirel. But the Lord Protector's faith is of Claumgnor the Grey Shadow, an altogether more productive deity. The Lord of Smoke and Toil rewards his followers well, unlike the useless Patrons of yesteryear! When finished, this site will produce arms and armaments fit to equip ten full legions a year. You're welcome to take a look! All who labor assiduously are welcome in the Halls of Smoke."
More stuff about Claumngor. Sounds like Augustine is playing an RTS. Too bad, this is a JRPG and you got the genre wrong. (Well until we start nationbuilding seriously.)
You have awakened 3 Signs of the Empyrean Mantle, whose domain is all magics entire; sun and moon and stars and the unblinking void beneath.
These are the themes of the Opalescent Tower. Very ZK. Magic + Sky versus Mundanity + Earth...
They harbor artifacts that would work perfectly with your style of magic. The Tower itself is forged of the same material as your incomplete Cloak of Sky.
This clues us in as to why we were capable of absorbing the Tower. Now, I kind of expect us to not be able to absorb the Tower of Earth... Frustrating. However, I'm realizing now that we might eventually have to deal with a Contest of Primacy for the Sky, since we now know that it can be developed independently (and presumably there's a capstone benefit for being the Most Sky).
Sticking his hand out a window, the air was cold and harrowing, sharp contrast to the delightfully comfortable atmosphere within. Some invisible barrier truncated the two realms, despite their lack of physical separation; within and without as clearly divided as the sun and the moon by the sky.
Some interesting contrast to the Tower of Earth. Sky makes people comfy, Earth has a "fell radiance" that "swarms mind and spirit".
The Evening Sky trailed avidly behind him, swishing across the floor-stones like a calligrapher's brush. Sky-folded opalescence swept into its embrace as it moved, leaving a trail of bleak mundanity behind.
Without the magic, the Tower is just a tower.
At the end of this, I propose a few tactical ideas from my findings:
1. Look for ways to smooth over the inherent animosity between elements. Perhaps use Edeldross or Taffyamber to hold them together, or something.
2. The inherent risk of Abduction (The forceful seizing of another's armament, inconsistent in applicable and terribly risky, as aspects of the prior wielder may impose themselves upon you. The hero stole into the Tyrant's Catacomb and emerged bearing the sword of the Tyrant's progenitor. That blade now lies broken, and with it its wielder.) is that aspects of the wielder may impose themselves upon us. Resist mightily with our Will stat and also force it to compete with Sten's mental contamination and Forebear's thick musk.
3. The seams of azure and gold probably don't have a connection with Gisena's ring, but it's worth it to try.
4. Maybe we don't have to absorb it into our Cloak. Maybe we can absorb it into our Sword? (which is made of STEEL!)