I do not know what "of such" means in the following quotation:
“Of such great powers or beings there may be conceivably a survival . . . a survival of a hugely remote period when . . . consciousness was manifested, perhaps, in shapes and forms long since withdrawn before the tide of advancing humanity . . . forms of which poetry and legend alone have caught a flying memory and called them gods, monsters, mythical beings of all sorts and kinds. . . .” —Algernon Blackwood.
Googling for the meaning of "of such" does not help, as Google returns definitions of "such," ignoring "of."