… AND FINALLY, AN ALTERNATIVE THEORY OF THE DRAGON’S CONTINUITY
As the Impurity / Heresy Dragon was some kind of offshoot of the Sestren AI, it presumably knew about the nature of these crests, as it seemed to know about many other things. Thus, what I conclude happened at the end of Zwei was that the Impurity decided to preserve some remnant of Lagi - the noble, good-natured beast that bore it - inside the Dragon Crest, when it became evident that the physical being was going to die. I will come back to this point in a moment, after introducing a more fitting example; the origins of Edge’s Dragon from Panzer Dragoon Saga.
Assuming that, for the reasons discussed above, Edge’s Dragon is not the same dragon from PD1, the obvious question of its origin arises. However, I think that the Dragon Crest on the bottom floor of the Excavation Site ruins is heavily implicated in all this.
If the purpose of a Dragon Crest was to store an actual dragon in the Ancient Age, it seems perfectly feasible that there could be Dragon Crests around the Continent with actual Ancient Age dragons inside them. If this was how dragons were stored, it would also explain the Empire’s sheer inability to find even a non-functional specimen in the present time.
If the Impurity / Heresy Dragon was left bodiless again after the events of PD1, is it so far fetched to assume that, being an energy-data offshoot of the Sestren AI, it would have the ability to activate a Dragon Crest in order to make it download its contents? If Edge’s Dragon was a standard Ancient Age dragon downloaded out of that Dragon Crest in the ruins, and taken over by the Impurity / Heresy Dragon, it would explain quite a few things. Of course, it gives a reason for why the dragon and crest are both coincidentally at the site; but it would also explain why the dragon looks so different in Saga, and why it has to start morphing - via a different evolutionary route - into the Blue Dragon / Solo Wing.
As is stated in the games, the dragon was the ultimate living weapon developed by the Ancients, and this was presumably well-known by the Impurity / Heresy Dragon when it was ejected from Sestren prior to Zwei. After all, why else would it choose to mutate a creature - Lagi the Coolia - into that specific form? The answer is of course, because to Sestren’s knowledge - and so to the Impurity?s knowledge - that was the most powerful physical form available. From the way the Impurity always seems to strive towards the Blue Dragon / Solo Wing form, I can only conclude that on top of the dragon being the most powerful creature designed by the Ancients, the Blue Dragon / Solo Wing was the most powerful dragon designed by the Ancients.
Anyway, to return to the theory, I believe that the Impurity stored some kind of data-copy of Lagi inside Shellcoof’s Dragon Crest in order to in some way preserve him, despite the actual Lagi dying, as Lundi states. This would explain why the dragon pup in Saga seems more like an essence, or a caricature of Lagi, rather than the real him.
Following that, there seems to be a lot of events missing between Zwei and PD1, by anybody’s reckoning. Lundi’s diary necessitates that the Impurity must have found another body in this time; maybe it mutated another Coolia, maybe it found another dragon in a Dragon Crest, or maybe it acquired one through some other means. What is clear is that by the time Kyle encounters the dragon for the first time, it has already had some kind of a journey; time enough to acquire and bond with a new rider, (our mysterious Sky Rider friend,) and time enough, it seems, to evolve whatever body it found into the Blue Dragon / Solo Wing form again.
At the end of PD1, when it presumably exhausts itself in destroying another Tower, it seems that the Impurity was separated from the dragon again, and eventually settled on the body stored in the Dragon Crest below Saga’s excavation site, as discussed above. In the course of Saga, the Impurity downloads the copy of Lagi stored in Shellcoof’s crest, and through that process at the Red Ruins merges with it, both helping it to re-attain the Blue Dragon / Solo Wing form and also letting Lagi live on as a part of the physical dragon.