Vikings' Seer appears to Christian warrior Jarl Kåre in Netflix's Vikings: Valhalla, but why is he the only Kåre he can see?
Jarl Carr announced that he had visions of The Seer in Netflix's Viking's spinoff Vikings: Valhalla, a fact his Christian companions (including King Olaf) seem to have a hard time believing. Seer is the only Valhalla character to return from the original series, albeit as a shadow of a man who died long ago. The series has always embraced the possibility of the divine, with Ragnar himself claiming to be descended from All-Father, Odin, but whether or not Kåre's brushes with The Seer are the intervention of the gods is somewhat unclear.
Ayraah first appeared to Fredis in a dream during her time in Uppsala, the spiritual center of the pagan Viking community. Kåre shares a similar view of Freydis, with The Seer appearing shortly before the plundering of Uppsala. Both warriors have brief encounters with the deceased fortune-teller as they lick the fortuneteller's palm and inquire about their fate, but only Carr claims his visions still exist, and they speak of them to Olaf during their siege of Kattegat. Although Carr insists his visions are real, neither the public nor Olaf has shown evidence for them (except for his first vision in Uppsala).
The simplest explanation for Carr's visions is that he is insane, driven into delusion by the imperfect knowledge given to him via prophecy. Carr effectively says the same thing, reluctant to share all his visions with Olaf for fear of looking crazy. As a child, a hater watched how his older brother was sacrificed to the gods in Uppsala, which had a lasting effect on him and laid the foundation for his hatred of pagans and his ferocious conversion to Christianity. Carr's guilt may be nothing more than a manifestation of Carr's guilt, but the similarities he shares his vision with Freddies suggest it could be something more.
Freddy's and Carrie's Visions of the Vikings: Valhalla relates to the prophecy of the "Cross with the Sword", a title which seems to have had a claim. One of Carr's visions that appears to the audience ends with him asking him about his fate, but the answer he receives never appears in reality. This was immediately followed by his destruction of Uppsala. Perhaps the Sir appeared to tell Carr that he was not the cross to hold the sword, which prompted him to violent outburst and fueled his need to prove himself in the eyes of his god. Each subsequent vision of Carrie of the seer maybe just a delusional madman trying to convince himself of a fate he knows is not his. The prophecy could also be ambiguous, but Carr took from it what he wanted, and read in it enough to justify his destruction of the pagan holy place and all the priests in it.
It's hard to say for sure whether or not Kåre (or Freydis, for that matter) encountered the seer's soul. The show has always ceased to merely affirm the supernatural, despite the many inexplicable events taking place within it. It seems likely that The Seer will appear again in Vikings: Valhalla Season 2.