One Hell of a Hike!
This one is an ass kicker! It definitely had me rethinking my hiking decisions. Go clockwise on the loop! (Opposite of what AllTrails shows.) Steeper route up is better than down. There are several checkpoints on the way up, to help you get to the goal: Mitchell Rock, Twin Peaks, Eagle Peak. Finally, the summit of Mount Diablo. The miles of not-technical fire road on the return loop is easier walking after an already long and strenuous day.
Thank you for recommending going clockwise. I’m a big fan of doing the difficult, more exciting parts first, then coasting the rest of the way =]. Plus, the experience of crossing the ridge from Twin Peaks to Eagle Peak was amazing going this way. Thanks & congrats on completing the challenge.