In Accursed Kings (GRRM has lifted a lot from this series for ASOIAF and endorsed it as the original GOT), there is a fortress called the Castell’Ovo, which exists IRL.
Legend goes that Virgil (yes, the poet) placed in the base of the fortress a magical egg laid by the mermaid Parthenope, who tried to entrap Odysseus with her siren's song. Odysseus had himself tied to the mast of his ship in order to avoid being bewitched/driven insane by her singing. The legend of Castell’Ovo alleges that if the egg is discovered/broken, then the fortress and Naples will fall.
Castell’Ovo stands on a rocky little isle off the coast of the city of Naples. It looks a lot like depictions of the Hightower. Further, in Accursed Kings, Naples is portrayed as a mix of Sunspear and Oldtown, more akin to Oldtown in that it was a centre of culture and had great influence on the election of the next pope.
The legend and depictions of the Castell’Ovo made me think of the Hightower’s fused black stone base, Euron’s impending attack on Oldtown, and the bit of prophecy about waking stone dragons/waking dragons out of stone/great stone beast taking wing from a smoking tower.
Salladhor Saan remarks that “if the red woman brings them [the dragons] to life, the castle will come crashing down, I am thinking.” Here, he is referring to the stone dragons on Dragonstone but it echoes the legend of Castell’Ovo.
However let’s go to Oldtown first.
So, could there be a magical egg(s) or a sleeping stone dragon/beast in the bowels of the Hightower base? Is the fate of Oldtown tied by magic to ensuring this “treasure” remains undisturbed in the base of the Hightower? Perhaps Euron learned about this during his travels. He can kill two birds with one stone, literally —get a dragon and destroy Oldtown at the same time.
So how will Euron wake the stone dragon/beast/hatch the egg in the Hightower base?
The iron figure at the prow of the Silence:
“Victarion's gaze was drawn to the iron figurehead at her prow, the mouthless maiden with the windblown hair and outstretched arm. Her mother-of-pearl eyes seemed to follow him. She had a mouth like any other woman, till the Crow's Eye sewed it shut.” (AFFC, The Reaver)
Curious how a mouth on an iron sculpture can be sewed shut? Victarion thinks the eyes are following him, because maybe they are? I don’t think the iron sculpture is merely a decorative element. I think it’s another artifact Euron found in Essos (Asshai?).
Euron will “unsew” her mouth (or awaken her) and once unsewed/awakened, the iron maiden(!) will emit a melody to wake/hatch whatever is inside the Hightower base (=stone beast/dragon), which will emerge through the always-lit Hightower beacon (=takes flight from a smoking tower). It’s a twist on Odysseus’ mermaid myth, with the maiden at the prow of the ship singing a melody to bring forth doom.
Now, how did Euron find the iron maiden?
The band Iron Maiden happens to be from Leyton, a suburb of London. Could this allude to a control/origins relationship between the iron maiden at the prow of the Silence and Leyton Hightower? Of note, one of Iron Maiden's songs is Lord of Light and the lyrics include references to fire, Lucifer, Others, fly(ing), shadow, burning bodies, darkness, among other buzz words.
Could Leyton have been the one to sponsor and guide Euron’s travels, tasking him to find the iron maiden (but not necessarily telling Euron what it was for--which he figured out later)?
Baelor Blacktyde spent 8 years in Oldtown as a hostage after the Greyjoy rebellion (~290-298) and returned converted to the Faith of the Seven. Baelor Blacktyde hated Balon Greyjoy, so perhaps he introduced Euron to the Hightowers after Balon exiled him in 297?
Then, look at Victarion’s description of the crew of the Silence:
“On her decks a motley crew of mutes and mongrels spoke no word as the Iron Victory drew nigh. Men black as tar stared out at him, and others squat and hairy as the apes of Sothoros. Monsters, Victarion thought.” (AFFC, The Iron Captain)
Eustace Hightower reported seeing monkeys that walk like men in Sothoryos. Could Sothoryos monkey-men be immune to the effects of black stone structures? Making them ideal to field a crew going to Asshai. Perhaps Leyton instructed Euron to field his crew with Sothoryos monkey-men based on knowledge passed down via Eustace Hightower because Euron would need to go Asshai.
Was this enterprise spurred by whatever Leyton and Malora have been cooking at the top of the Hightower since 290, i.e. they figured out where the iron maiden was located, discovered a way to control whatever would emerge from the Hightower base without causing the fall of Oldtown?
Further, as this post theorises, could Malora fall in with Euron? Become his iron maiden? Is her moniker the Mad Maid a hidden allusion to her being “madman” Euron’s girl?
Additionally, Garth Hightower is called Greysteel, which (1) could be a play on words with Greyjoy and ironmen/Iron Islands, and (2) is synonymous with Greyiron, as in the ancient dynasty that ruled the Iron Islands before being toppled by the Hoares and Greyjoys. Could there be an ancient familial link between the Hightowers and the Iron Islands via the Greyiron kings (thus explaining a common origin for the Seastone Chair and Hightower base?)? An allusion to a Greyiron vs. Greyjoy rematch?
TLDR: Euron may have been sent by the Hightowers (via Baelor Blacktyde) to find the iron maiden artifact that is on the prow of the Silence. Euron will unsew the iron maiden’s lips to unleash her siren's song to bring forth a beast/dragon from the stone base of the Hightower. Inspired by the real life legend of Castell’Ovo, Oldtown may fall due to ancient magic tying its fate to keeping the beast/dragon/egg undisturbed in the stone base of the Hightower.