πρόφρων κραδίη καὶ θυμὸς ἀγήνωρ
At both 10.220 above and 10.319 below, the formula ἔμ’ ὀτρύνει κραδίη καὶ θυμὸς ἀγήνωρ (“my heart and audacious spirit rouse me”) is used when Diomedes and Dolon, respectively, respond to the call for a spying mission. Here, Diomedes says that he is choosing Odysseus as his partner in the mission because his heart and audacious spirit are ready and eager for all kinds of labors; these personal qualities of courage and boldness are what impel men to go on nighttime or spying missions or on ambushes. We can compare the opposite in Achilles’ denunciation of Agamemnon in Iliad 1.225–228, when he says that Agamemnon has the heart (κραδίη) of a deer and never arms himself for war or goes on an ambush with the best of the Achaeans, enduring it in his spirit (θυμός). It is clear that there is a deep-rooted association between these qualities and the daring feats of these types of missions. See also on 10.231 and 10.248.