In Aeneid VII.10-24, how does Virgil make his description of Circe's land menacing?

Throughout this passage, a foreboding and menacing atmosphere is masterfully evoked by Virgil. From the very first sentence of this passage we are on tenterhooks, with the delaying of the verb 'raduntur' until after we are presented with the locale of this passage of action - 'Proxima Circaeae' - having the effect of telling us where we are, but leaving us unclear until later what precisely is going on. It is disorientating, captivating, and terrifying. Then, Virgil provides us with our first in-depth description of Circe's island, with a sentence that runs with no end for 4 lines -- an entirely encompassing experience, overwhelming the reader's imagination with such description and detail with no abating, which has the effect of completely drawing us into the menacing aura of Circe's land. In these lines, one might also note the present participle 'percurrens' to give a sense of immediacy to the description. A similar tactic of run on lines, for the same purpose, is again employed in the directly preceding lines, 15-20, in which, to examine these in more detail, one might start by looking at the delaying of 'leonum' in line 15: again, Virgil is expert in building up atmosphere and tension through a line direct toward a certain word which ties the entire meaning together and is thus furnished with greater emphasis. For, in 'exaudiri gemitus iraeque leonum' we are first given the verb, telling us that something (we do not know yet what) is heard; then that it is a groan. Here, we might expect to find out who or what is groaning, yet we are delayed again with iraeque, the pejorative and telling word choice creating greater foreboding, before we are finally told that these groans and angers are those of lions, with 'leonum', in its end of line position, becoming all the more frightening, and further emphasising the otherworldly -- or, at the very least, exotic -- nature of Circe's island. The next two lines, which detail more of the wild beasts that throng on Circe's island, are made all the more emphatic through the repeated, hissing, sibilance: saetigerique sues...praesaepibus ursi/ saevire. The final four lines of this passage are also remarkably interesting from a grammatical point of view: the result clause is actually put first, 'ne...subirent', before stating what Neptune did 'Neptunus...vexit', again, to show the scary, foreign nature of Circe's land, and to make us all the more glad when we get to the description of Neptune's intervention, and rescue of the Trojans.