I bred Diamond and Olympus some time during the night, didn't check the breeding time, but still have around 43 hours left. Verified that I did, in fact, use Diamond and Olympus, so it looks like I got it on my first try! Shocked, because I STILL don't have Valiant - and I have tried breeding him tons of times! Even with the Diamond temple!
Yay for Achilles! :-)