Actually, a lot of names in Greek myth start with delta, but…Diomedes is the one I know the best, so he’s going to be easiest for me to talk about quickly and get back to work.
Of course, there are actually two different men named Diomedes in the major Greek myths. One is a Thracian king who owned mares that ate human flesh, and the usual end of his tale is that Heracles feeds him to those mares while he’s fetching the horses as one of his labors. He’s not the one I want to talk about. (Though it’s worth noting that the cruel tyrant Diomedes is a son of Ares, who was strongly associated with Thrace, and sometimes even said to live there. The heroic Diomedes has little divine blood.)
The Diomedes I’ll be talking about is one of the heroes of the Trojan War. His father was Tydeus, one of the Seven who marched against Thebes in the bitter war between the two sons of Oedipus. (Interesting fact: in some early versions, the children of Oedipus had not been fathered on his wife/mother. It was probably only the tragedies of the Athenian stage that made that become the dominant view. (Though I admit that I’m not sure which version the fragmentary Theban epic cycle presents…)) Anyway, because of that, Tydeus died while Diomedes was just an infant, so he never really knew his father. But–like his father–he was a favorite of Athene, goddess of wisdom and warfare. Because Diomedes wasn’t just a powerhouse on the battlefield, he was also a clever thinker.