I think the comic strip is based off a real event that happened during the void century. Unlike what we are led to believe, Sora probably wasn't a member of the WG. I can say this because until recently, Germa kingdom was associated with the WG. So I think there's probably a high chance they were part of the 20 Kingdoms that fought Joyboy.
Rather I think Sora was a marine, not on Imu's side, but on the side of the ancient kingdom. The robot in the comic was none other than this dude.
And the seagull? I think it is this:
We know that Poseidon is a living person, Shirahoshi, and it controls living things, the sea kings. We know that Pluton is a purely mechanical creation, a warship that franky once had the blueprints for. What if Uranus is a combination of both, a cyborg creature? An artificial life form perhaps?
Shiki said that Roger knew the location of an ancient weapon. But this meeting was before Oden joined the crew so I doubt Roger's weapon was Pluton or Poseidon, as he couldn't read the poneglyphs.
Rather, I think Roger's weapon was the seagull. We saw that he had a giant egg on the orojackson, I'm guessing that was the egg of the uranus seagull.
I'm guessing that the seagull can be fed energy to make it stronger and that by giving it a piece of mother flame, the WG was able to make it strong enough to destroy lulusia.
