This is Djose Temple, the third temple and is lightning-based, like Kilika was fire-based. You get to watch a rather impressive orbiting rock field around the temple itself. Don't forget to look left past the bewildered Chocobo Knights for a chest containing 4000 gil and another with 4 ability spheres behind the building on the right before entering Djose Temple. Inside you'll meet Isaaru, another summoner, who is quite different from Dona. Once you get control of Tidus, you can check the left-hand side of the stairs to the Cloister of Trials for an Ether, and the side room on the left contains a Remedy. But in the right hand side room you can find a Mega Phoenix — which is really useful in a tight spot. Once you're finished you can ascend the stairs to the Cloister of Trials, but Isaaru will return and inform you of an important rumour first.
Djose Temple: Cloister of Trials
This temple is a bit longer and more difficult than either Besaid or Kilika. Anyway, first things first, take the two Djose Spheres out of the side slots and put them in the slots on the door to open it and trigger a section of the large glowing Yevon symbol up ahead to light up. Head on through. In the next room, the glyph on the door doesn't do anything, so remove the Djose Sphere connected to it and place it in either of the two slots between the unreachable Glyph Sphere and the pedestal on the ceiling. Take the other Djose Sphere powering one of the sections of the Yevon symbol and put it in the other slot. Now, leave the other Djose Sphere in the moveable pedestal and push it along until it's directly underneath the pedestal on the ceiling. This will supercharge the Djose Sphere in the pedestal.
It's now powerful enough that you can put it in the door trigger slot, and it'll open, but only for as long as that sphere remains in the slot (the other Djose Spheres aren't powerful enough, and you can't supercharge more than one of them). Beyond the door will appear to be a dead end — a large painful lightning field and endless drop between you and the other side. Shoving the pedestal into it doesn't work (if you try this and lose the pedestal, simply stand on the shining glyph on the left-hand side of this room to get it back — the pedestal is obviously made of pretty tough stuff). What you need to do is put two more Djose Spheres (and not the one holding up the door) into it, then shove it into the lightning field. They'll cause the pedestal to float back up, and miraculously act as a platform for you to cross the gap! Hop across and push the pedestal on the other side containing a Djose Sphere into its slot, powering up the inner "eye" of the Yevon symbol.
You need to light up all the sections of the symbol. First of all, use the shining glyph to get your pedestal back. Take the two Djose Spheres from it and put them in the side slots in the first room. This will power up the two side bits of the Yevon symbol. For the last bit around the "eye", take the supercharged Djose Sphere from the door-triggering slot, and put it in the other spare slot that you found one Djose Sphere in to begin with (on the left-hand side of the door to the lightning field room). The pedestal will disappear, and a lift will appear on the symbol. But don't go on it just yet — go left to where the shining glyph is and touch the pulsating glyph on the wall. The wall will rise up, revealing the Destruction Sphere. Take this, then stand on the lift to be taken up to the next floor of the temple. Head up to the room ahead, and push the five pedestals into their respective wall sections. Another pedestal will appear in the centre of the walkway between here and the lift, where a wall has risen to reveal the exit staircase. However, you'll want to put your Destruction Sphere in the pedestal, which will blow a hole in the supposedly blank wall, revealing the Destruction Sphere treasure for Djose Temple; a Magic Sphere. This creates a Magic +4 node on the Sphere Grid which can then be activated by a Mana Sphere. Now, you have finished the Cloister of Trials and can enter the antechamber and get your next summon by walking up the staircase.
Talk with your party up here, and you'll get to see Dona again. Woo. Once that's over you can try to leave to trigger Yuna to reappear from the Fayth room. You'll rest, and get a new aeon! This one is Ixion, the lightning-based summon. Once you awaken you'll be outside Djose Temple, waiting for Yuna. You can't leave this area to the south to trigger her appearance this time, so head inside the Temple and into the left-hand side room. Speak with the priestess at the top right and Yuna will wake up. Once you've got control of Tidus again head into the building on the right and you'll find a Switch Hitter in the chest in the back now that the man has moved out of the way. Save, then follow Yuna back along the bridges and to the junction. Next up, it's the Moonflow.
After you get the Airship, return to the Cloister and enter the Chamber of the Fayth after completing the trials get a cutscene (+ a fortune sphere) and open some treasure chests containing a Magic defense sphere and an Evasion sphere.