Why is Xerath still bound by his coffin?

Something just came to my mind as I was reading a thread discussing Renekton's madness.

Xerath has ascended, right (Sorry if I'm wrong, I was a old lore lover and I can only muster half a fuck to give about this new one), honest-to-goodness, somehow-not-animalesque ascended? Then what are those bits of metal floating around him now?

In the old lore, they were his sarcophagus, as the old mages of Shurima had bound him to, afraid of his power. It was what kept him in check, power-wise, and stopped him from absolutely destroying half the League's champions single-handely at the same time.

But I don't think his imprisonment in the new lore involved Nasus and Renek sealing him into a sarcophagus, just sealing him, right? Otherwise, Renek wouldn't have to go all cliché "GO MY BROTHER, I SHALL SACRIFICE MYSELF TO CONTAIN THIS BEAST" and go mad over it. So, what exactly is that armor and why does it carry it around instead of proncing about as the being of pure, arcane energy he is? What, do the Ascended get offered a free armor from the sun too? And what exactly is the excuse for Xerath being equal power-wise to the rest of the League? He's an Ascended so powerful it took two Ascended to contain, not even destroy, CONTAIN!

And while we're on power levels, I was always under the impression Old-lore! Nasus and Renekton were equally as powerful as the rest of the League (Berserk-style freakout in Renek's Judgement nonwithstanding) because they came from a dimension where magic, runes and weapon/armor enchantments were very rare or non-existant, and as such creatures as Nasus and Renek passed as gods, while in Runeterra's dimension they were considered top-tier, sure, but at the same level of other champs and uber-powerful magicians, much more common.

But in these new lore, they are literal Physical Gods. How do they manage to lose to normal humans such as Graves, Miss Fortune, Ashe, Olaf, Sejuani, etc? Again, in the old lore, their dimension probably lacked guns and magical/runic enchantments (Ashe's bow, Sejuani's mace, most armors and weapons champions use), so it was normal to think they were gods, but now they're from this dimension! Excluding guns, everything champions use (Magical weapons/armor and boring old magic) was present during the time they were worshiped as Ascended! Why aren't they moping the floor with the other champs 1vs9?

Freaking hell, I miss the old lore.