Alright, we’ve gone over what we know for sure about Lion 3: Straight to Video. Now it’s time to get down into the speculative stuff. There’s a Chekhov’s Gun just waiting to be fired, and probably some more foreshadowing for stuff that will be more fully revealed later.
The battle flag
Starting off with the lesser of the two curious items, let’s talk about the flag that was flying by all of the items left in Rose’s stockpile. It was clearly a symbol of Rose Quartz: both the flag and the pole it was displayed on were pink, and both were decorated with a flower. The flag even included brambles, like Rose had at her healing spring.
This is an interesting find. While Lion 2: The Movie showed us that Rose kept her own secrets from the Crystal Gems, it had been easy to assume that Rose had started the Crystal Gems before doing anything interesting on Earth. This flag, clearly associated with just Rose by herself, when considered along with Watermelon Steven for another interesting possibility: Rose Quartz initially stood along against the other Gems on Earth, only attracting the others to her cause later. The Quartz Cave may very well be a private redoubt that fell into disuse after she created the Temple with the others.
That Rose Quartz initially stood alone brings up the possibility that the other Crystal Gems were initially enemies of Rose Quartz, or at least meant to be. It was already implied by Alexandrite’s design that Amethyst, Garnet, and Pearl were a group before they met Rose, and as Gem warriors they would naturally go wherever there were enemies that needed to be faced.
The other big item in the hoard is a bubbled gem. The gem is pretty clearly a bismuth crystal, but that doesn’t really give any hints about what it’s doing there. Whatever it is, though, it’s probably not too dangerous. The other Crystal Gems don’t seem to know anything about this place, and Lion can’t accompany Steven to the hoard. This means that Steven is meant to encounter the bismuth gem alone, and him accidentally popping it wouldn’t be beyond his abilities to handle.
It’s possible that Rose bubbled an ally to help further train Steven, but that’s exceedingly unlikely. This Gem would have had to be bubbled for thousands of years, or else have avoided notice by the Crystal Gems for a really long time. Even then, there’s no good reason to bubble a friendly Gem to wait for a decade or two when Pearl seems to regard such a time as appropriate for a short jaunt to the next star system.
Much more likely is that Bismuth is a Gem who was corrupted into a monster, like all of the others. The gem would have been bubbled and placed into the pocket world to be found by Steven because it was the one Rose came closest to healing. If Rose expected Steven to be better at healing the corrupted monsters than she was, and Monster Buddies made it pretty clear that he was, she would consider it vital that he master the skill, and what better monster to try it on first than the easiest one? Since Steven already has some experience with the Centipeetle, healing Bismuth will probably prove even easier than Rose anticipated. Look out for Steven to make a new friend some time late in the season.