'Elision' is most likely the act of "hiding one's Voice" (c.f. the use of the term in linguistics) from the Agencies of the Outside, rather than the act of seeking Oblivion per se. Of course, the former seems to be a necessary (but not sufficient) prerequisite for succeeding at the latter.
The Deepest Deep is doubly interesting, because in Nonman metaphysics geographic depth is associated with the past. The implication may be that the Nonmen were not always damned, and that one of the theoretical approaches to seeking Oblivion lies in recovering that lost past (perhaps by de-evolving one's soul to a pre-sapient state, hence becoming invisible to Judgement just as animals are?)