Diamondback Gulch is where Sedona jeep tours stop being scenic drives. This private 2.5-hour run drops into and climbs out of a deep desert gulch west of Sedona — steep, rocky, genuinely rugged terrain through high-desert country most visitors never see, with wide Verde Valley views from the rim.
It's private, so the guide reads your group: full-send for thrill-seekers, or a notch down if the group wants the scenery with slightly less airtime. Either way, this is the tour people mean when they say "extreme."