Green Lantern Corps #4

John Stewart and a handful of other Green Lanterns are taken prisoner by the aliens. They're brought back to the aliens homeworld where they must cross a vast expanse called the Emerald Plains. The entire way has imprints of Green Lantern Batteries.

Okay. So these aliens have some sort of sick obsession with the Green Lanterns. Like I thought earlier, their homeworld has most likely been devastated due to the Lanterns somehow.
Back on Oa, Guy Gardner is trying to find out some information from one of the beings they took captive. He isn't getting anywhere until Martian Manhunter shows up to read the alien's mind.

As you can see by Gardner's reaction, he has no idea who Martian Manhunter is. So either Martian Manhunter has never been known by any of the heroes of Earth or else all the heroes of Earth have had their memories of him erased when Manhunter joined Stormwatch. Since I won't be reading Stormwatch for a few weeks, I'll just have to wait to find out. But Manhunter extracts all of the information they need about these aliens.

Manhunter finds out that these beings call themselves the Keepers. They were in charge of keeping the Green Lantern's power batteries safe back when the Lantern's used to reach into some subspace pocket for them when they needed to recharge. But at some point, the Oans said there was a problem with the wormhole technology and made the Lanterns responsible for keeping their own power batteries safe. So the Emerald Plains must have been where the batteries were stored.

Manhunter also finds out that the Keepers are headed toward Oa to take the Central Power Battery. So that must be what devastated the planet! They were probably using the power batteries themselves for their worlds needs. It was possibly their primary fuel source. And when the Lanterns took them away, their economy and their world structure just collapsed around them. So now they're using the wormhole technology to steal resources to rebuild their world. And they're also coming for the main power battery for their ultimate fuel source.

Not a bad story idea to come out of the question where did the Lanterns used to keep their Power Batteries! And then extrapolating from there to think about a planet that actually relied on these batteries themselves!

Four issues in and I believe seven Green Lanterns have died. I haven't been keeping a very accurate count and I'm not sure Porter actually died. But that's a pretty good start!