Right now I'm inclined to believe it's Shiva - otherwise the Gigas (tentative name) tribe has no primal, whereas the Sahagin do; and both were shown in the concept (along with what we believe to be Siren). It looks to me like ice reaching upwards, and we see a few major differences - no face paint, inclusion of ears, and what looks to be a black collar where Siren has smoothed green plumage.

Right now I'm leaning towards (but not trying to propagate) the idea that a primal is messing with us... encroaching on The Twelve's territory. Remember, the Echo has nothing to do with the Seventh Umbral Era or the Grand Company's storyline. The Echo is part of the main scenario, which has a very different focus. Every single mission drills it into our heads - The Echo might not be from The Twelve, the primals darken your heart and make you violent and should never be allowed corporeal form, over and over. I think that one is trying to gain support with us, and that we're going to have to resist it as we've resisted the others.

But that's for another thread in another time.