Eren could tell that Reen and Asura were different from other Elder Seed Artifacts.
Asura was a demonic saber that carried the consciousness of the Demon Prince of Wrath within it. However, for some reason, Eren could not interact with Demonmir the way he was used to interacting with Shallot or Reen, the two artifact spirits.
Demonmir had indeed been transformed into an artifact spirit by Eren. However, Samael had managed to isolate his spiritual connection from Demonmir at the very last moment, turning Demonmir's consciousness dormant.
It was as if Demonmir had been robbed off of logical thinking and all the sentiments that turned him into the existence known as Demonmir. Only his primal instincts remained with him after turning into an artifact spirit.
