Which preposition to use with afterguard

as Occurrences 1%

Note 6, p. 32.It may be added that in contradistinction to the nicknames of Skipper conferred upon Evans, and Mate on Campbell, Scott himself was known among the afterguard as The Owner.

of Occurrences 1%

" Dull, gray wisps of murk, the afterguard of the gaseous cloud, were twisting and spiraling in a witch-dance across the landscape, and, seen by snatches and glimpses through it, something flapped darkly in the breeze.

Which preposition to use with  afterguard