Maybe the Covenant who warned Linden to remember that he's dead was the false Covenant. I mean, if the idea of a false Covenant is plausible at all, why can't it be the voice in her head, rather than the person she sees at the end of Runes?I would assume that the appearance of this false Covenant is exactly why covenant warned Linden to remember that he's dead.
Wayfriend's GI quote (which was a fantastic, forgotten gem to recover!) seems to make it plain that Covenant is not dead. If he's like Caer Caveral, then he's merely transformed. And Foul is trying to mislead Linden by perpetuating the idea that Covenant is dead. In one sense, this is true: he's dead in the real world. So she's spent 10 years living with this as a fact. Perhaps Foul is relying upon that habit of thinking to mislead her, to blind her to the fact that things are different in the Land. So when Covenant finally appears, she'll mistrust him--just like we all do (hence all the "false Covenant" speculation).
There was a bit in that quote not emphasized by Wayfriend. Let not overlook this:
This is a strange way to describe what happened to him. When someone dies, their mortality reaches its culmination--it does NOT get destroy. It gets fulfilled. The person gets destroyed, not their mortality. Mortality is the possibility or inevitability of being destroyed. So in a sense, Covenant wasn't killed as much as he was made "immortal."In Covenant's case, the destruction of his mortality freed his spirit to support the Arch of Time. . .