Mages are Nietzchean Overmen, able to see through all illusions, break down any hinder and create whatever worlds they want. But the most chilling thing is that they often are right. The final step is the ultimate sacrifice. The mage must be not only willing to sacrifice his power, his body, his mind, his soul and his individuality to Ascend, he actually has to do it. The final step towards Ascension is the death of the Ego, which will irrevocably vanish forever.
Nobody knows what comes afterwards, or even if there is anything but Oblivion after the final step.
This fills most mages with total fear, and many won't undertake the final step, instead proclaiming themselves as Ascended and perfected while they really are incomplete and filled with hidden fear of the unknown. Instead of dying, their egos grow and become perverted with power and understanding, until they are farther from Ascension than even the Sleepers. Only those who boldly dare to risk total annihilation can truly Ascend.