I decided that, while writing The Darkest Hour, I would post some theories I come up with on the Legend of Spyro. Any way here's my first one:
Malefor's Corruption
Isn't it strange how Malefor, one day, just decided to go to the dark side for no reason? One day he's the savior of the Dragon Realms and the next he just decides to murder everyone. Here's the thing though, we see this exact thing happen to Spyro in Eternal Night and in Dawn of the Dragon and same with Cynder in the New Beginning and DOTD. I am, of course, talking about Dark Form. What if Malefor is under the influence of Dark Form?
There are three pieces of evidence suggesting this other than the sudden change of heart. First off is the size of Malefor. It is suggested that Malefor is just as old as the Guardians. So why does he tower over them? We have seen a case like this before. Cynder. In A New Beginning she is around the size of the Guardians while she is only around 9 – 12 years old. This is due to Dark Form. Malefor used his powers to artificially turn Cynder into her Dark Form. We know this is Dark Form because Malefor turns her into her Dark Form at the end of DOTD. Anyway the reason this is relevant is because, in ANB, Cynder is the same size as the guardians. It seems that prolonged exposure to Dark Form causes one hell of a growth spurt.
The next piece of evidence is coloring. When a dragon enters Dark Form, their scales become black and eyes become white. However, it seems that prolonged exposure to Dark Form changes your appearance (as seen with the size). I believe that after staying in Dark Form for a certain period of time it will revert the dragon to their original scale color except with a darker tint. This is shown, again, by Cynder. While in her Dark Form she has Black Scales and a Crimson Underbelly. However when she is reverted back to normal she has Dark Gray scales with a Magenta Underbelly. Compared to Spyro, Malefor has a similar color palate except it is darker. Dark Purple Scales with an old-looking Yellow underbelly compared to Spyro's Purple and Gold.
Finally the greatest piece of Evidence, Elements. Malefor, along with Spyro and Cynder, are the only Dragons we know of able to use Convexity. Convexity has been associated with Dark form many times over TLOS. It is first shown during the Cynder battle during ANB and then shown again when Spyro enters Dark Form in Eternal Night. Both times involving Dark Form. This leads me to believe that Convexity can only be used by Dragons either under control or can control Dark Form. Further proof of this is in DOTD. Instead of Furies, it allows you to use Convexity for a short period of time. This shows it is possible to use Convexity outside of Dark Form. This means that even if you did say that only Purple Dragons and Dragons under control of Dark Form could use Convexity you would be wrong since Cynder can use it outside of Dark Form.
In conclusion, evidence points to Malefor being under control of Dark Form.