θείου παρὰ σήματι Ἴλου
From the geneaology of the Trojan royal family that Aeneas tells Achilles at Iliad 20.213–240, we learn that Ilos was the son of Tros, the father of Laomedon, and grandfather of Priam. His name is related to the name of Ilion. His grave mound acts as a landmark on the Trojan plain: both its prominence and the adjective θείου suggest that it was the site of a hero cult for Ilos (see Nagy 1979 on hero cult and the Homeric epics). This landmark also appears in two other episodes related to ambush. In Iliad 11, Paris hides behind the stele on the grave mound as he shoots an arrow at Diomedes (Iliad 11.369–383; at Iliad 11.372 Ilos is called Dardanos’ son, perhaps meaning descendant, or perhaps reflecting a different geneaology: see Gantz 1993:557–558 for the question). This grave mound acts as a landmark again at Iliad 24.349, when Priam journeys to the Achaean camp to ransom Hektor’s body. After they pass the grave mound, Priam and his herald stop to water the horses and mules at the river, and it is there that Hermes meets them (see “The Poetics of Ambush” for both of these episodes as related to the ambush theme, and also 10.1ff. for Priam’s night journey). That Hermes meets them at this point suggests that Priam is then in a dangerous space and needs protection (as Thornton 1984:154 also observes). The grave mound is also used as a landmark during the daytime fighting: when Agamemnon routs the Trojans, they pass by this grave mound (Iliad 11.166) and then the fig tree as they move to the city. Thornton identifies the features of the Trojan landscape, in order from the walls of Troy to the ships of the Achaeans as: “the oak-tree of Zeus, the fig-tree, the tomb of Ilus, the ford of the Scamander, the “rise” or hillock on the plain, and the Achaean ditch or wall” (Thornton 1984:150; see also Hainsworth 1993:243 on Iliad 11.166 for this grave mound’s place in the Trojan landscape). Thus we can see that the Trojans are rather close to the Achaeans on this night, and that the fearful thoughts Agamemnon has at the beginning of Iliad 10 are justified.
The spatial information Dolon gives here in terms of this landmark will recur in even greater detail in his subsequent answers. Spatial indications are important to ambushers moving through the darkness. (See also Clay 2007 on spatial indications in descriptions of battle in Homeric poetry.)