User blog comment:Princepurple/Some Questions/@comment-26271908-20160602194756/@comment-5583089-20160603140602

on 2. when Cain or dean died, due the mark, they became demon's, no corruption required, the usual rules applied likely where not for like, evident by dean dying and simply coming back, so most likely, Lucifer did not cause Cain to become a demon on death, as he certainly didn't for dean, it just happened, the darkness, directly bore two very powerful demon's, from within probably their own vessels (probably for cain) without the thousands of years in hell.

Amara's corruption maybe different, simply because as Lucifer say's.. raw power, no experience, unlike lucifer, she didn't direct her power, this corruption just seemed to be raw and wild...

If other angels had the power to do so, why not do it? it just seems very odd that the form of a spirit is of light, similar to an angel essence, or God, it's bright, and luminous, Lucifer Himself has this form, but upon corruption, it's essence shifted to be dark and smokey, like the essence of the Darkness.

So far in the show, not counting crowley's, all demon's smoke form is very similar to the darkness true form, before Lucifer gained the mark and corrupted souls, everything that had been created (all souls and essences) where of the light, seems odd that when corrupted they become dark... the only other example are leviathan's, though they themselves could have been corrupted early in their development by the darkness.