Alright time to hit Bevelle. They're hiding something and we gotta know. So we arrive and well easy walk through the front door. See its worth it giving them the sphere.
So on the way down. FIENDS ARE IN THE TEMPLE! Wait wut? Well let's keep moving. Bahamut's gone??? Wut where? Down the giant hole that was made and we find a weird factory, security system, thing. Well here's our first major activity.
Deactivate the Security System and get the Ribbon
This can be a long one. First off we need to turn off all the annoying alarms. We do this by approaching those towers. There's 2 sub bosses you gotta fight. Familiar faces are they not? Once everything's activated. You can do some optional exploration to get some treasure or move on ahead. But I want that Ribbon.
So to get the ribbon you need to arrange all the platforms you activated to go down in a counter-clockwise fashion. Each tower controls a particular extra platform while the Red ones IIRC control how they move. Forwards, backwards, or mirror. Use this properly arrange your platforms till you reach the very bottom. Your reward is a great accessory. The ribbon.
How I did it will be shown in part 2. But once you figure it out it's not too hard. You may also want to keep messing with the towers to oversoul our 2 familiar friends since they can't be found anywhere else.