So, I have two *maybe three* major candidates for this Legendary Hero banner, and they're pretty close IMO.
First has to be Corrin, she/he is a water dragon and a clear stone could fit him/her pretty well . Plus, Corrin from either gender needs a bump up, hard.
Second is F Robin and with recent posts I have seen the silhouete from the Acrylic figurines as well as the relation to the other two heroes and I have to say that it could be her. I don't think she'll have a levin sword though, since Ike is still here for this banner. I think she could potentially be the first clear mage unit, or a clear dragon (maybe she uses the book of Naga?) and is the antithesis to our recently added Grima.
And last but not least, the clear dragon is a story character. The lead units are heading towards Gunthra in some shrine, and I could see Gunthra hanging around with Fjorm's other sister (she could be the dragon) or a potential Tiki situation, where Alfonse and the rest learn of some prophecy and meet the dragon that will help them.
I have those three in mind, but I can't think of any other's. I doubt that if they would add F Robin as a Grandmaster that it would be as a red unit, considering Ike is around plus the acrylic figurines. Corrin could be possible, whole grey waves plus they need a buff, and the last option is totally speculation like the rest of this post.
Opinions? I wanna hear em, cause I really want to see what the community (in Gamepress) actually thinks about this.