But there was another detail in the episode that could actually be much more important than it first seemed. Hal used something called the sentry protocol, which allows his Green Lantern ring to create an identical hologram of him. And now people are wondering whether this strange little ring feature could have much bigger implications for Hal, John and the future of the DCU.

So, what actually is Hal’s sentry protocol?

We first saw Hal’s ring create a version of him earlier in the season, when John discovered the Halogram hiding inside the ring. Episode 5 then revealed that this isn’t just some random hologram. Hal can actually activate a feature called the “sentry protocol” and send the Halogram out to investigate things for him.

Hal activates the protocol while watching over Rushville and sends the holographic version of himself to track down Zoe. The Halogram can then move around and investigate while the real Hal deals with other things.

The feature is especially useful because Hal is trying to find Zoe while also dealing with a town under attack. Instead of having to be everywhere at once, he can send his digital double out to investigate. And that is a pretty useful trick for a Green Lantern.

The Halogram could be more important than we thought

Basically, the Halogram is a backup of Hal’s consciousness combined with the sentience of the ring. Green Lanterns are supposed to update these backups regularly, which explains why this version of Hal exists inside his ring in the first place.

And that makes the whole thing much more interesting now that Hal’s fate is such a huge question. Could the sentry protocol explain what happens to Hal?

Well, at the end of episode five, John defeats Hal and takes his ring. Hal is then left behind after Zoe’s attack, while John eventually gives the ring back to Guardian Lianna. We also know that the story eventually jumps forward to 2026, where Hal’s fate becomes one of the show’s biggest mysteries. So, the Halogram could somehow become important to that story.

There is already a theory that the Hal we see later might not be the original Hal at all. Some viewers have even pointed to the Spanish subtitles, which label the injured Hal as “Clone de Hal”, or “Hal clone”. That has led to speculation that the sentry protocol could be connected to whatever happens to Hal.

And what does this mean for John Stewart’s ring?

John does actually get Hal’s ring after defeating him. He even puts it on. But instead of keeping it, John gives it back to Lianna. John tells the Guardian that Hal “betrayed everything to keep this ring” and that it “broke him”. He then says Hal probably does not even remember why he wanted it in the first place. And then John basically realises that he doesn’t want to become the same person.

So, now the major question is who gets the ring next?

Well, we already know that Nathan Fillion’s Guy Gardner is a Green Lantern in the DCU, including in Superman. Lanterns co-creator Tom King previously explained that one of the central mysteries of the show was exactly this: Why Guy has the ring when the series is focused on Hal and John.

So, the show has now created a very believable gap between Hal’s time as Earth’s Lantern and Guy Gardner becoming the Lantern we see elsewhere in the DCU. That doesn’t mean we’ve seen exactly how Guy gets the ring yet. But it does mean John’s decision is directly connected to the mystery the creators have been building around Guy.

Also, the really interesting thing is that John is not being written out of the Green Lantern story just because he rejects the ring. Aaron Pierre is set to return as John Stewart in Superman: Man of Tomorrow, alongside Nathan Fillion’s Guy Gardner.