Does the seeker do anything at all, or even appear again after this chapter? If not, it is an entirely unnecessary detail. It feels like a homage to a story Paolini hasn't written yet. If he had written the story of the Seeker first, then this appearance would be an "oh, cool!" callback.

Instead, I am instantly reminded of a different entity from a different franchise: the Destroyer, from the Marvel movie Thor. Not so much in appearance, but in presence. Mixed with the mind stone sceptre thing that can mind-control anyone it touches.