The game picks back up at the fire pit which is the same location where the intro scenes to the game occur. Head over to the Save Sphere and save your game before you follow the rest of your team into the Zanarkand Ruins.
Follow the pathway along straight into Zanarkand - the pathway is fairly linear. There is a treasure chest along the way that contains a Fortune Sphere. There is a small platform/walkway even further on down the path with another treasure chest. It contains a Spiritual Targe.
The entrance to the Dome has a Save Sphere off to the left side. Save your game before you head in and then make your way towards the entrance. There is a short cutscene involving a man at the front entrance speaking to Yuna. Proceed into the Dome after this scene.
Move forward down the pathway. Make a U-turn once you come out of the other side of the tunnel and proceed along the upper pathway. There is a treasure chest at the top of the pathway that contains 10,000 gil.
Continue moving forward until you reach the next Save Sphere and save your game. Just past this area is a scene involving Seymour. Go down the pathway to the right (eastward) to find a treasure chest that contains a Friend Sphere.
When you see the image of Lord Braska, Auron and Jecht pass by make sure you turn around and follow the pathway down to the lower level. There is a treasure chest at the bottom of the path that contains a Lv. 3 Key Sphere which is a very rare item.
Go through the doorway up ahead and into the next area (listed as the corridor on the menu screen). There is another treasure chest off to the right side that contains a Luck Sphere. Follow the images of Lord Braska, Auron and Jecht up to the top of the stairs. Save your game using the Save Sphere at the top of the stairs and then proceed into the Zanarkand Cloister of Trials.
Before you rush into the next area to confront Yunalesca there is an upcoming boss fight which you may want to prepare for. You will not be dealing with the Berserk status effect anymore (so you can remove any armor you had on previously with ‘Berserk Ward’ or ‘Berserkproof’). Instead, you will be dealing with the Blind status ailment if your characters perform regular attacks and the Silence status ailment for magic casters. This means that you should equip any ‘Blind Ward’ or ‘Blindproof’ armor you have on your melee characters (Tidus, Auron, Wakka and Kimahri) and ‘Silence Ward’ or ‘Silenceproof’ armor on your magic casting characters (Yuna and Lulu).
Boss Battle: Yunalesca
There are three phases to the fight against Yunalesca and she will take three different forms during the course of the fight.
Yunalesca has two counterattacks that she will use during phase one. If you attack her with a physical attack she will counterattack that character by casting Blind on them. If you attack her with magic she will counterattack by casting Silence on that character. You have two options: you can use Yuna’s Esuna spell to rid yourself of these status ailments or you can use items to remove them (Eye Drops for Blind, Echo Screens for Silence or Remedy for either). You can also have Rikku use Al Bhed Potions to remove the Silence status effect and do some healing at the same time.
Yunalesca will now use a move called Hellbiter during the second phase of the fight. Hellbiter will inflict the Zombie status on all of your party members. Following this, Yunalesca will begin casting curative spells on your party which will inflict damage while the Zombie status effect is active. Your own healing spells and items will also cause damage. If you remove the Zombie status effect from all of your party members Yunalesca will immediately reuse the Hellbiter spell, so keep the Zombie status effect on at least one character at all times. Have Yuna use Esuna on a character if you need to heal them. Have Yuna also cast Dispel if Yunalesca casts Regen on any of your party members.
Yunalesca can now cast a spell called Mega Death. Mega Death will instantly kill your characters unless they are afflicted with the Zombie status effect. This is another reason why you must keep Zombie active on at least one character at all times.
Additional notes and strategies:
Holy magic is incredibly powerful against Yunalesca and you will likely require Yuna in your party for Dispels, etc. Have Yuna blast away at Yunalesca with this spell to wrap up the fight easily. You can easily have Yuna (or Rikku) learn to cast Holy at this point in the game by using a Teleport Sphere or a Return Sphere and a Lv. 3 Key Sphere. Rikku’s standard path goes right by Holy as shown in the screenshot below:
Use Yuna’s Reflect spell on your characters to reflect the status ailments back to her during the first round and to reflect Regen back to her in the second round. Just be aware that you will want to have Yuna cast Dispel on Yunalesca if she casts Regen on herself so that she does not heal herself for much HP.
Yunalesca will use a move called Punch which will remove all positive status effects with the exception of Reflect, which makes Reflect an incredibly powerful tool during this fight. You will want to cast Reflect on Yuna to make sure that she cannot be silenced during the fight.
Equip your characters with armor that has abilities for negating Silence, Blind and Confuse, but be cautious about negating the Zombie status effect. You will want to keep Zombie on at least one of your characters.
Go to the back of the area where you fought Yunalesca and descend the stairs that lead downward. You will be teleported to the other set of stairs on the opposite side of the room. You must to this step in order to make a treasure chest appear at the back of the room. This treasure chest contains the Sun Crest which is used to create Tidus’ Celestial Weapon called Caladbolg.
Go back down the stairwell that was used to enter this room for another cutscene. Save your game at the Save Sphere and then exit the Zanarkand temple.