The books are easily returned.

Scouring the ice fields for one man is not so easy. There's nothing out here that can threaten the two of them, but the ice is large and uneven.

Eventually, though, they spot a rickety little boat in the distance, pulled up against a rare spit of land.

First interesting thing so far. Maybe it'll even be what they're looking for.

There's a massive rock on the island, and, when they reach it, a tiny door is barely visible in one of the cracks.

"Hopefully this's him, and not some other nutjob," Ena mutters.

"I fear for the future of this world if there is more than one person insane enough to live out here."

Snort.

Onwards into the cave of dubiousness?

Onwards.

There's an icy ramp down through the rock, that then opens into a small cavern carved from the stone and ice. A large Dwemeri cube with a strange lock sits against one wall. A man in dark robes paces below, muttering to himself - "When the top level was built, no more could be placed... It was and is the maximal apex..."

"Septimus Signus?" she calls.

He reacts only somewhat. "What voices are these that come to me?"

"The kind with people attached." She walks down into his field of view.

"And what has brought this wind across the sea to me?" he asks, not really looking at them.

"Questions."

"Oh? What will the wind sing? My feet were set upon the rock, but it turned to mud and drew me down."

"Do you have an Elder Scroll?"

"Their fabric is all around us. The warp of air. The weft of time. It is not in my possession, but it is nearby. It is all nearby."

"Where?"

"Here. Well, relatively speaking. Mundus. Tamriel. Everywhere and nowhere."

She sighs in frustration and rubs her forehead. "Where, specifically?"

"One block lifts the other. Perhaps ourselves could help us each."

"That would be easier if you would stop speaking in riddles."

To Ena, "Come down and look through his things while we're talking."

There aren't many things to look through, but Ena does step down and examine them.

Septimus makes no move to stop her, instead saying, "Septimus will give you what you want, but you must bring him something in return." He gestures over to the strange box. "You see this masterwork of the Dwemer. Deep inside their greatest knowings. Septimus is clever among men, but he is but an idiot child compared to the dullest of the Dwemer. Lucky then they left behind their own way of reading the Elder Scrolls. In the depths of Blackreach one yet lies. Have you heard of Blackreach? 'Cast upon where Dwemer cities slept, the yearning spire hidden learnings kept.'" He starts laughing, then, a bit manically. 

"How can we get there?"

Ena starts flipping through his books. And then finds his field journals.

Septimus continues with: "Under deep, below the dark. The hidden keep, Tower Mzark. Aftland. The point of puncture, of first entry, of the tapping. Delve to its limits, and Blackreach lies just beyond. But not all can enter there. Only Septimus knows the hidden key to loose the lock to jump beneath the deadly rock."

"You know, you didn't have to write your journals in verse, too," Ena mutters. Septimus ignores her. "It looks like the Scroll's in a tower in the southern side of Blackreach, a hidden Dwemeri city. There's multiple entrances across Skyrim, but the only one he's found is the Aftland one. There's actually multiple keys, probably one for each entrance, but they'll be hard to find. He's not our only option, but he's the one standing in front of us, so."

"What is the key?"

"Two things I have for you, two shapes. One edged, one round. The round one, for tuning. Dwemer music is soft and subtle, and needed to open their cleverest gates. The edged lexicon, for inscribing. To us, a hunk of metal. To the Dwemer, a full library of knowings. But empty. Find the tower and its sky-dome. The machinations there will read the Scroll and lay the lord upon the cube. Trust Septimus. He knows you can know."

He hands them a metallic sphere engraved with Dwemeri runes. "This is the key. The deepest doors of Dwemer listen for singing. It plays the attitude of notes proper for opening. Can you not hear it? Too low for hearings?"

Then the cube, more elaborately engraved: "To glimpse the world inside the Elder Scrolls can damage the eyes. Or the mind, as it has to Septimus. The Dwemer found a loophole, as they always do. To focus the knowledge away and aside without harm. Place the lexicon into their contraption and focus the knowings into it. When it brims with glow, bring it back, and Septimus will be able to read it for you."