DreamWorks TV just released a new video with a little more information about the next season of Race to the Edge! In that past, many of us have speculated that Heather's belt contains a dragon eye lens. Although the video doesn't say for sure what will be on it, this is the first time that we've seen any kind of acknowledgement of it (3:21).
The Race to the Edge team also said that the Dragon Eye will be a "major part" of the next season and that it will lead the Vikings to new dragons, such as a "baby version of an old favorite" and a "species of albino dragons" (4:06).
The video also suggests that the Dragon Eye's gas defense and gear system may have influenced the Zippleback gas weapon on Hiccup's future sword, Inferno, and Hiccup's prosthetic leg (1:45).