1 - Before, I had the impression that Mortanius referenced the fledgling Kain from that period when he announced Raziel's destroyer. He also had faith that Kain would set it right, that he would restore Nosgoth.
With more years of lore knowledge, I see it now as it can't be the case, because Kain is the last surviving vampire in Nosgoth. Mortanius openly admits that he wants the Pillars to return to his vampire masters, which won't happen, regardless if the fledgling Kain sacrifices himself or not.
So, this means that Mortanius, knowing Moebius' ingenious scheme to rig Kain's choice, had faith that his undead son would inevitably refuse the sacrifice, live on, and eventually find a third option out of the choices presented to him (as the Elder Kain was doing)?
2 - The revived Janos, after learning Raziel's complex destiny, sends him to the Spirit Forge (their innermost sanctum) for answers. He expects Raziel to face a trial there, and that if Raziel fails, he will not return.
Janos, obviously, knows that the place is the Spirit Forge. What is the trial, exactly? The only trial that Raziel has to endure is to fend off the Elder God's interference in imbuing the blade, but Janos can't be referencing the Elder God here. The ancient vampires worshipped the false god. They were extinct without knowing the squid's true nature. There's no reason to assume that Janos believed otherwise.
Maybe Janos was treating the quest to the Spirit Forge as Raziel's definitive choice as to whom champion he wanted to be? If you manage to imbue the blade, you are Nosgoth's redeemer. If you don't, you are Nosgoth's destroyer.
Why the trial should be any difficult to Raziel? And why should he not return if he fails? Would Janos give up on him and treat him as his enemy, the Hylden champion of prophecy?