The Dweller. Prophet. Statistician. Sometimes madman. It is unclear, even to himself, whether he is seeing the future or calculating probabilities better than the fastest computer in existence. Needless to say, The Dweller knows things, often before they happen.
Of course it could be Ekur or one of the other Ancients as well. I don’t think she would be intimidated with Ian at this point, so for him to pipe up wouldn’t be much of a threat in her mind. My guess is that it’s one or more of the other Ancients.
Calliel really is losing touch if she, despite her association with the Dweller, takes his words as a threat. The man can predict the future; he’s trying to warn her away from her …
Meant to say: He’s trying to warn her away from her death.