Something happened to Lord Drakon between the second and third season.
In the second season, Lord Drakon gave Rixel a time limit to capture Onchao and/or Ono, but throughout that season, he never really clarifies why he wanted the winged unicorns so badly. In the third season, he wants the golden horn of either Onchao or Kyara so he can regain his physical form. Given that he seems more focused on the horns rather than the wings this season, it may indicate that his goal is different from what it was in season 2.As for what exactly happened, perhaps something was happening to Lord Drakon during season 2 that would eventually cause him to lose his physical form, and he needed Ono or one of his descendants before the next full moon came around to prevent this, which is why he gave Rixel that time limit. With Rixel failing, and Lord Drakon losing his physical form, he instead shifted focus to obtaining the golden horns, since their incredible power could restore his body.
