So, in this image of Culdee Fell...
We see a younger Gregory Larson (with a heck of a great head of hair! XD) conferring with a random, unimportant dude (yeah, for sure), next to a mysterious engine on the hoist, appearing to be a model
of Belle repainted black. However, for a fraction of a second, we see this image...
In this one, there is another engine on the hoist, which I believe to be a repainted Gator model. Anyways, where am I going with all this? Well, the two engines you see here aren't super important to this current topic. What we really want to focus on is the people here. So, there's Larson, yeah, but who's the other dude. Well, here we go...
In the credits of Culdee Fell, we see Gregory Larson playing his signature guitar. Beneath him, we see a view of the Smelter's Yard where we observe the shadowed figure of Sir Frederick Aura playing the same song on a similar guitar. So, this practically proves it: Larson and Aura have some sort of connection. But what is it?
Remembering back to Munitions and Swashbuckler, we recall that Aura is an avid fencer. If we look back to Snow Blind, we notice that the Thin Controller is taking fencing lessons from whom we later discover to be Gregory Larson. During their duel in Swashbuckler, we see that the Thin Controller and Sir Frederick Aura are very evenly matched when it comes to fencing. With that said, is it too hard to assume that Aura may have also received lessons from Gregory Larson as well? Well, let's take another look at the first two images. Looking at the hair of the unidentified man talking to Larson, well, its style and color is akin to that of Aura's, which we got a look at in Swashbuckler. So, perhaps that man with Larson is in fact Sir Frederick Aura.
Or maybe it isn't. Maybe it is... Frederick Larson. Yeah, you heard (or rather read) me! Here's a theory: maybe Gregory Larson and his son Frederick (oh yeah), were working together to build some sort of special engine (seen in the first image), but then Gregory hired another helper. Some guy by the name of Roger Sam (hey, remember this: "I've had a nosy controller meddling in my affairs for far too long..."). Gregory's relationship with Roger Sam starts to push Frederick out the door a little bit, so Frederick quits the project and builds his own engine (seen in image two). Whatever he did was impressive, because he was knighted for it. Angered that his son abandoned and surpassed him, Gregory disowns Frederick. Frederick then changes his last name to Aura (because honestly, is not Aura a pretty amazing name for a villain?), and tries to get revenge on both his father and Roger Sam. This eventually leads to some more stuff, and then more stuff, and... this is as far as I've got.
Another piece of evidence, just to support how Larson is not to be trusted, here's this. After the credits in Culdee Fell, Edward goes to visit Douglas, who's nearly done with his overhaul. Douglas has another outburst about diesels, despite having his aggression settled back in This Too Shall Pass. He claims to just be a little out of it after his repairs. Okay, sure, but this has never happened with any other engine after an overhaul, and Edward fully acknowledges that "something is very, very wrong." Well, no one ever lost memory or anything before Mr. Larson became the chief engineer! I don't know why he would want to mess with Douglas' mind, but who knows?
All I know for sure is this: Aura and Larson are connected somehow. Larson is not what he seems. Aura's got a big bone to pick with the Thin Controller.
NOTE: This is a theory, and is not canon to EE93's series... or is it? ;)