Gemhearts

[Honorless]

So, we learn from Leshwi that the ancient Singers apparently did something to anger the spren, current-day spren seem to be much more fine with the Singers, with such a long gap without Desolations and the memory of the Recreance, plus the fact that most of the older spren became Deadeyes during the Recreance.

Moving over to the Sibling, they are not fine with fabrials, even though the modern-day spren are fine with it, as fabrials employ non-sapient spren. Fabrials employ gemstones to capture spren... which is also what the Singers do to change their Forms, they capture spren within their Gemhearts.

We've seen other creatures with Gemhearts before in the series, notably we've seen the process of Gemheart extraction when Eshonai pulls the Gemheart out of a Chasmfiend.
Chasmfiends use spren bonds with Mandra or Luckspren so that they are not crushed by their own weight. These spren are seen flitting around Chasmfiends as well as other Greatshells like the Tai-Na

[minor Dawnshard spoilers]

Spoiler

and apparently the Larkin & Lanceryn.

We also see them around Skyeels, iirc, who probably use their bond with them to fly.
Similarly, Musicspren seem to flit around the Ryshadium who might be in a bond of some kind with them. Though Ryshadium don't have Gemhearts.

Spren can be captured in gems the same as Lights because they are made of Investiture.

Is the purpose of Gemhearts really to capture spren? Because it would seem you can bond spren without trapping them in Gemhearts. They are attracted to natural phenomena and emotions... and the Rhythms. We saw the Dawnsingers seemingly Stoneshaping by using the Rhythms. We saw Lifespren responding to the Rhythms. Spren, like the Investiture they are made of, respond to the Rhythms.
We saw other creatures that have gemhearts and need spren bonds, and they didn't seem to trap spren within their gemhearts. The spren were flitting about freely with them. They extract gemhearts from the Chasmfiends but did they ever find a Luckspren trapped within their Gemheart? We saw Eshonai extract a Gemheart from a Chasmfiend but there was no spren within it. (Would the spren be free upon the creature being killed or only if the gem itself is cracked?) What if the Dawnsingers originally used their Gemhearts to store Light?

What if the crime that the ancient Singers committed against the spren which angered them was this? Trapping spren within their gemhearts to change their Forms.

[+Aletus]

I think of it more of a Rosharan specific biology. But I'm not sure how I feel about that thought. My biggest thing is Venli and Timbre, Timbre seems to chill in her gemheart, and it seemed to be pivotal in her bond, but I don't think he's trapped in there, like if Timbre was in her gemheart and she broke her oath, I don't believe he'd remain, unable to leave. So maybe taking the spren to change forms was a big deal because it's a perversion of the biology that allowed for a nahel bond to happen. I could definitely see that. 

[Aon Tia]

I can buy that argument. Simplest answers are the best answers. 

[CogitoErgoArclo]

I don’t know if I agree that they “capture” spren within their gemhearts. I think it would be more accurate to say they form a symbiotic bond with a spren that resides in their gemheart. 
Because the spren is benefiting from its time in the gemheart. It influences the Singers mindset and form, so that they are more likely to engage in activities that bring about the emotions or natural processes the spren is drawn too/feeds off of. 
 

[Honorless]

4 minutes ago, CogitoErgoArclo said:

I don’t know if I agree that they “capture” spren within their gemhearts. I think it would be more accurate to say they form a symbiotic bond with a spren that resides in their gemheart. 
Because the spren is benefiting from its time in the gemheart. It influences the Singers mindset and form, so that they are more likely to engage in activities that bring about the emotions or natural processes the spren is drawn too/feeds off of. 

Hmm I don't think I've ever heard anyone think of it like that. The Singers themselves think of the process as capturing spren within their gemhearts. And that's what Artifabrians do with gemstones too

[CogitoErgoArclo]

Ah, but we only hear about capturing them from the Listeners. Who deliberately cut themselves off from their culture and history. So I think their conceptualization is inherently flawed, which is why it was so hard for them to find new forms. 

[shawnhargreaves]

There's definitely something different going on with gemhearts vs. fabrials.  When Navani captures a spren in a gemstone, it's trapped until she does something explicitly to release it (afaik breaking the gem is the only way?) but Ulium can come and go from Venli's gemheart as he wishes.

This could be as simple as Navani is using cut gems while a natural uncut gemheart is less 'perfect', though?