Final Fantasy X/Macalania Temple

Jyscal's Sphere
Once you enter Macalania Temple, save, then talk with Tromell who will thank you for saving him and allowing him to escort Yuna safely to the temple, and will give you a Shell Targe for Rikku. Walk forward, and you will get a cut scene with Shelinda. The scene will differ slightly depending on if you told Shelinda on the Thunder Plains that Yuna and Seymour were getting married or if you said they weren't. Check around the room for two chests on the sections around the outside of the room. One contains 5000 Gil, the other 2 X-Potions.

Afterwards, approach one of the side rooms. A temple acolyte will stagger out of one of the side rooms, and say that she found a sphere of Lord Jyscal Guado in Yuna's belongings. Before following your party, check the other side room; there are 3 Phoenix Downs at the back in a chest, and you can talk to the guy eating just beside it to receive an Ether. Enter the room the acolyte came out of and you will view the sphere's contents, which tells of Maester Seymour, Lord Jyscal's son, and Jyscal's murder. Check the chest at the back of the room for 2 Remedies and talk to the yellow-clothed person at the back of the room to receive 2 Hi-Potions. Leave the room and enter the Cloister of Trials (which at the moment is only a frozen bridge, you will have to complete the trials on the way out) to view a scene with Auron, Wakka, and Lulu. Cross the bridge into the next room. After an edgy talk with him, you will have to battle Seymour and his Guado Guards.

Boss Battle: Seymour
This battle has a few difficult features to it; Seymour is no less potent than he was when you used him to defeat Sinspawn Gui. He has 6000 HP, whereas his Guards have 2000. The battle will begin with the 2 Guards casting Protect on themselves and Seymour casting Shell on himself, which halves physical attacks and magical attacks respectively. Change your party to Wakka, Tidus, and Yuna and use their "Talk" trigger commands to double Tidus' Attack and double Wakka and Yuna's Magic Defense. Next cast Haste with Tidus on Yuna, then switch Tidus out for Rikku and Wakka out for Auron.

Someone should have a weapon with Sensor equipped — if not, use the Weapon change option to do so. This way, the handy Sensor information bar will tell you that Seymour has a nice predictable attack pattern which goes ice, thunder, water, fire. So, you should make note of this order and have Yuna repeatedly cast the appropriate Nul spells so that Seymour cannot inflict any damage on you. However, any non-magical attack against Seymour will be blocked by his Guards, and if you attack them, they will heal themselves, faster than you can kill them. They also have a Shremedy attack, which inflicts confusion on one character (you have to hit them to knock them out of it, or use one of your precious Remedies). Don't worry though; this is why Rikku is out. Have her Steal from both the Guado Guards to disable their healing abilities, then just obliterate them with magic from Lulu (switch Rikku out for her once you've stolen from both of them, but you can also nab a Turbo Ether off Seymour). Once both Guards are dead, pound Seymour with attacks. When he gets to low health, he will summon his Aeon, Anima, to deal with you. It is important however that you do NOT use any summons for this stage of the battle and that all of the characters that will reappear after the next part have all four Nul spells on them and Yuna is in Haste. Do not kill Seymour until this is the case, otherwise once you reach the end of this chain of battles you will die.

Boss Battle: Anima
Anima looks tough, and most importantly, is tough. The only attack it will use against you until Overdrive is Pain, which inflicts a good amount of damage but most importantly, instant death. Fighting Anima with just your normal party will end up with you being systematically killed faster than you can revive yourselves. So, the absolute first thing you should do is summon your new Aeon (named Shiva). Aeons are immune to instant death and so she'll be able to take Anima's Pain without too much trouble. Use Blizzara on her when her HP gets low to replenish it, and keep attacking normally and with Heavenly Strike until her overdrive is full (it'll charge much faster than Anima's). Then, use Diamond Dust for a lot of damage. Your Aeon should be doing at least 8000 damage with Diamond Dust; if she isn't, then level up Yuna more at the next earliest opportunity and use the Magic Sphere you have (if you haven't already) on Yuna as any improvement to her stats will boost all of her Aeon's stats in the same area. The fact that Anima alternates between using Boost and Pain helps to keep your new Aeon alive during the turns that she loses from using Diamond Dust. The only problem is that Anima must die before its overdrive is full because Oblivion will do a large amount of damage but if your aeons are strong enough then shelding should stop your aeons from dying. Inflict the 18000 HP damage you need to kill it, then Seymour will enter the fray once more (and likely one-hit your new Aeon with an -aga level black magic elemental spell).

Boss Battle: Seymour…Again
Now Seymour will be back at full health (6000 HP) and you must fight him again. The only differences this time are that he has no guards (even if you didn't kill them the first time) and uses 4 new deadly spells called Multi-Fira, Multi-Blizzara, Multi-Thundara, and Multi-Watera, which involve him casting said spell 2-3 times in a row, hitting multiple characters and doing a whopping 800-1000 damage with each. But you were a good reader and casted all those Nul-spells before, didn't you? Keep recasting them and Seymour will hopefully never land a hit on you. As a fail-safe you can also hit Seymour with Magic Break, which he succumbs to some of the time (it may not always work even though it won't show him as being immune to it). Also to really hit him home you can use your spare moves with Yuna to heal your party should they sustain damage, or better yet, run across and smack him in the face with her staff for an excellent 50 damage. After you kill him he will fall to the ground and be carried out by his Guado Guards.

Now you have a chance to name your newly obtained Aeon Shiva, and spend your sphere levels that you have acquired. Save your game. After exiting the room onto the ice bridge, it will disintegrate and you must enter the Cloister of Trials for real.

Macalania Temple Cloister of Trials
Macalania's Cloister of Trials isn't particularly difficult but it is a long and arduous process to get the Destruction Sphere treasure, which is crucial, since failure to get it now will require that you contest with one Dark Shiva later on in order to re-enter the trials. First off, go down the ice ramp to the floor. Take the Glyph Sphere out of the central column and place it in the pedestal. Push the pedestal along the ice to the pile of snow near the altar on the far end of the room. Then, push it towards the Macalania Sphere in its slot on the left side of the room (near the next pile of snow you can see). The snow will disintegrate and the pedestal will slide down a previously-covered hole into a room below. Here, remove the Glyph Sphere from the pedestal and place it in the left-most slot. This will cause another Macalania Sphere and a large block to move up to the top floor. Leave the Glyph Sphere where it is and go and pick up the Macalania Sphere that rose up out of the slot. Go back down and place it in the column slot down here to make one of the ice bridge sections reappear.

Go up and take the Macalania Sphere out of the end slot on the altar, then place it in the pedestal and push the pedestal left into the slot below the column, and another ice bridge section will reappear. To make the final one reappear, take the Macalania Sphere by the ramp down out and place it in the central column slot. Go all the way up to the ice bridge. If you want to get the Destruction Sphere treasure later and fight through Dark Shiva to get it, then head out using the ice bridge. Otherwise, step on the shining glyph to recall your pedestal and break the ice bridge section at the end. Push the pedestal down the slope and the glyph will shoot it across to the large snowpile that originally had the Destruction Sphere in it, converting one Macalania Sphere into it. Use the shining glyph on the floor below to call the pedestal back, use the Macalania Sphere you do have up here to replenish the snowpile. Push the Destruction Sphere pedestal into the snowpile, then use it in the slot by the ramp to replace the snow down to the bottom floor. Push the pedestal down here. Go down and take the Destruction Sphere out of the slot and put it in the first one on the left on the wall. This will get rid of a bit of snow at the front of the room covering the Destruction Sphere treasure chest, which you can open to get a Luck Sphere.

However, you now do not have enough Macalania Spheres to replace the whole of the bridge. Not to worry, the Macalania Sphere you lost can be retrieved. Take the Glyph Sphere out of the slot on the wall to the far left and place it back in the pedestal. Go all the way up to the ice bridge and use the shining glyph to get the pedestal up there. Push it down and the glyph will shoot it across and replace the Glyph Sphere with another Macalania Sphere! Use the shining glyph below to get the pedestal back, then move the Macalania Spheres around so you can get the pedestal down to the floor below (you've done it several times already). Push the pedestal to the right and it will slot back in the column and replace the end ice bridge section. To finish this puzzle off, take the Macalania Sphere out of the slot that makes the ramp and place it in the central column's slot to finish off the bridge. Now, you've got to be careful. Go up to the ice bridge but you must not, under any circumstance, step on the shining glyph up here. If you do, you will have to repeat the end section of the puzzle all over again as the snowpile will convert your third Macalania Sphere back into a Glyph Sphere. Once you're up, head along the bridge to the stairs at the end.

Getting to the Lake
You've been branded traitors to Yevon and now you've got a whole entourage of Guado trying to apprehend you. Approach the crowd and you and your party will break through. Outside the Temple, in the cavern, O'aka will be on hand to sell you basic healing items. At least the whole world isn't against you, eh? Save, then follow the path around to the outside, but beware as Guado will chase you and summon fiends to fight you if they catch you.

Providing you run the whole way not all of them will catch you. The Guado will have their trusty Auto-Potion ability again so bring Rikku out to use Steal and disable it. Use appropriate characters to take out the other fiends they summon once the Guado are dead. The Guardians may cast Berserk from time to time; this isn't a problem, just kill the fiend that's berserked before it next attacks. Once you're outside, stop briefly to level up your characters and use Hi-Potions and Yuna's Cura to heal the wounded. Up ahead, don't use the first ice bridge to cross over the gap; stay on the side you're on and follow the narrow path along the rocks. It's slightly shorter and there's a Level 1 Key Sphere in the chest at the end. Use the icicle to get across the gap. Before leaving this area heal everyone up again using the Save Sphere, and save too. Enter the frozen lake area once more to be confronted by more Guado, and another boss!

Boss Battle: Wendigo
Unfortunately Square believes that you cannot get a long enough chain of boss fights and so it throws in this last little one to finish off quite a heavily-populated chain of difficult battles. First of all, use the typical Steal trick to get rid of the Guado Guardian's auto-potion ability, and kill them off systematically. Bring out Auron as well though, to begin with, to use Power Break on the Wendigo. The first move of the Guado will be to cast Berserk on it, which raises its Attack to a ridiculous level, capable of dealing 2000 damage in one hit. Using a Remedy or Esuna on the Wendigo won't work right now as the next move they get the Guado will recast it. Get your heavy hitters out and mince the Guardians. As each of them die, they will cast Protect or Shell on the Wendigo as a last gasp, and you currently have no method of getting rid of these. However, now that there are no more Guado, you can Remedy or Esuna the Wendigo to get rid of its Berserk, then reuse Power Break and wear it down until it dies. Using Haste will speed this battle up a bit. You can use Dark Buster on it if it helps. Watch out though, the Wendigo is smart and has a nasty habit of repeatedly attacking your lowest-health character until they die; and for some weird reason it seems to get more accurate the lower its health gets. Bring in an Aeon if you're having trouble, their overdrives will bury the Wendigo's 18000 HP into the snow in no time (use a Grand Summon if possible).

One last note: when the Wendigo raises it's fist in a blocking stance, it will counter most attacks you throw at it, so stick to magic and other forms of attacking (like Aeon special moves or anybody's Overdrive).

Beneath the Ice
With its last breath, the Wendigo will punch the ice and you'll go through, into a cavern beneath the frozen lake, by the ruins of more ancient buildings from long ago. Go through and talk to all of your characters to get their opinions on what has happened. After a long talk with Yuna and the rest of your party about trying to make right what has happened, you'll gain control of Tidus who's back at the Save Sphere down here for some reason. Head back along past all your characters for now (talk briefly with Yuna first) and check the right-hand corner past Kimahri for a chest containing a Level 2 Key Sphere, and check the obscured chest to the left of Auron for an Avenger.

Talk with everyone if you want to; Kimahri has a hilarious line if you take it out of context. Talk with Auron at the end to advance the plot, then walk away from him to trigger the appearance of Sin, and you'll get whisked away into a cutscene and off to parts unknown.

Return
After you get the Airship, return to the Cloister and enter the Chamber of the Fayth after completing the trials get a cutscene and open some treasure chests.