[OB] Nahel Bond Question

[Naurock]

So I've been re-reading parts of WoK, and got to the chapter Wandersail where Hoid tells Kaladin the story about the island. When he finishes talking and leaves Syl starts talking to Kaladin about his ability to draw Stormlight (because Kaladin thought he was cursed to watch everyone die while he lived) and she says this:

Quote

“I’m behind what is happening to you,” she said, voice soft. “I’m doing it.”
Kaladin frowned, stepping forward.
“It’s both of us,” she said. “But without me, nothing would be changing in you. I’m … taking something from you. And giving something in return. It’s the way it used to work, though I can’t remember how or when. I just know that it was.”

Excerpt From: Sanderson, Brandon. “The Way of Kings.” Tom Doherty Associates, 2015-11-17. iBooks. 
This material may be protected by copyright.

What exactly is she taking from Kaladin? I have searched the copper mind about Nahel Bonds and the WoB database and don't see this discussed. Is she taking his ability to choose? Now as a Radiant he must protect? That's the only thing I can think of.

But this seems like it could have major implications in the future when the Desolations continue past Oathbringer and more Unmade/Fused join the fight.

[Calderis he/him]

First, sorry to be a stickler but

OB spoilers 

Spoiler

The Fused belong behind spoilers outside if the OB board. 

As to your question, she's not really taking anything. There's a symbiotic relationship. He gets Stormlight, she gets sapience in the Physical Realm. He doesn't lose anything by that, but she gains it from him. 

[IllNsickly he/him]

39 minutes ago, Calderis said:

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As to your question, she's not really taking anything. There's a symbiotic relationship. He gets Stormlight, she gets sapience in the Physical Realm. He doesn't lose anything by that, but she gains it from him. 

@Calderis nails it again.

 

When Syl (or any other Nahel Spren) crosses into the Physical Realm, they lose the majority of themselves. By Bonding someone, they establish a connection that allows them to Remember.

There are a few conversations between Syl and Kaladin and at least one between Shallan and Pattern that address this.

[Subvisual Haze]

Spren seem to feed on certain human thoughts or emotions.

[digitalbusker he/him]

"Taking" isn't probably the word she should use, but she's still not in her final form, so she's not yet fully beautiful and articulate.

She's definitely receiving something from him (sapience) and giving him something in return (cool powers), and you could argue that he wasn't ever given the change to affirmatively agree to that transaction, so in that sense she's "taking" something from him. But we have no indication that his capacity is reduced in any way because of what she's getting through the bond.

Think of Syl like a helium balloon that for some reason wants to stick around near the ground. She ties herself to Kaladin's backpack, thus gaining access to his mass, which is enough to keep her from floating away into the air. If he were standing on a really sensitive scale you might be able to detect the change due to the Syl-balloon's attachment, but in practical terms it's negligible. In exchange, he gets a spiffy balloon.