6 hours and 58 minutes. 10 stages.
I'm one of those players that NEVER gets lucky in the game. I mean NEVER. I don't get easy or multiple drops and it always takes me hours to get something rare to happen. I screwed up in the beginning and have no Zodiac Spear. Should I try to get it to pop in the Henne Mines? Well...no. I'm not that much of a completionist. Besides - why? I just killed the biggest doofus in the game.
First on a scale of difficulty: Omega Weapon is faaaaaaaaar and away easier than Yiazmat in my opinion. Finding Omega Weapon is more frustrating than actually defeating it. Omega's gone and I tell you it gave me a real sense of overconfidence.
OK. My primary team going against Yiazmat was basically Vaan, Basch and Ashe. Vaan had the Masamune (I wasn't slick enough to steal SQUAT from Gilgamesh beause I was too busy trying to live through that battle against him and his stupid mutt and forgot to steal...and knowing my luck it would take me weeks of attempts to even SPAWN a Bombshell yet alone get lucky enough for it to drop a Yagyu Darkblade). Basch had a Tournesol and Ashe had the Fomalhaut with Dark Shot. Grand Armor on Vaan, Maximillians on the other two. Circlet on Basch and Golden Skullcap on Ashe. No helm on homeboy Vaan.
Vaan has a Bubble Belt. Ashe and Basch have Ribbons...at least for now. And there is a reason.
OK - go into this fight with as many Hi Ethers, Chrono Tears, Remedies and Golden Needles that you can carry. (99) Go to Rabanastre and buy some Windbreakers from the Protectives shop there too. Ahh you want to know about Gambit Setup? Let me tell you there are a million of 'em. This is what I used:
Vaan: Ally any: arise and Foe nearest: attack.
The other two had the same stuff. Ally any: arise, Ally Vaan: decoy, Ally Vaan: reverse, Self HP<70% Curaga, Self: bubble, foe nearest: attack. Simple eh?
You have to do some manual stuff. It makes it more fun anyway. Watch Yiazmat for buffs especially if you've had to run away-save-and return. Dispel them manually. Expose Yiazmat too - periodically. If you feel like it - Bravery out, Berserk out (your tank hello), Protectga out your party to your heart's content - but don't make it automatic. If your MP gets low - Syphon it from Vaan or whoever your tank is. DO NOT USE SHELLGA. Sure you might think this is a fine idea but SHELLGA tends to make things like all the magic you try and use on yourself miss more often. Not what you want.
While you're hammering away at the beast keep an eye on the upper left corner of the screen. When the stinker starts to ready Cyclone - do a quick change-o into Windbreakers and as soon as the animation ends go back to what you had on. During the first 8/10 of the battle (at least for me with Collector's Edition) this goon used Stone Breath and White Breath. He didn't stop doing this until he had 4 bars left. This is why it is very important to keep ribbons on Ashe and Basch. You only want to be wasting your finite supply of Golden Needles , Remedies and Chrono Tears on one individual: the tank. Otherwise you'll burn thru 'em. Now of course the flip side of this is that I'm casting Bubble all the time burning up MP but honestly - I need the turns. Even with Windbreakers on: Cyclone will cause a Sap effect and it sucks to be using all your turn slots curing status effects because Yiazmat doesn't wait.
It is a heavenly idea to keep your ranger (in my case Ashe) on the stairs. I also make her my party leader too so if I need to run it isn't far.
OK this is pretty much rinse and repeat and then Yiazmat begins using Death Strike. Typically he'll KO your Lured character first but sometimes he'll get you. This is where your Ally any: arise gambit on the tank can come in handy. It will be Life from an unexpected place.
It begins to be a real turd around the last 3 to 4 bars. He cast Growing Threat. He uses buffs (which must be dispelled when you return to the fight) and then Cyclone (equip da Windbreakers) followed by Reflectga on your party (dispel it immediately). Always remember to Expose this beast too - it does help. Now that he isn't using White or Stone Breath anymore - you can ditch the ribbons and take on the Bubble Belts. The only status effect you'll have to concern yourself with is Sap and Remedies will take care of that issue as will Esuna. And anyway - at this stage of the game the chances are just great that Yiazmat will get you long before Sap will. Reincarnation is a cure for status effects.
Now listen. You have to have a stout heart because sometimes Yiazmat will use Death Strike often and for a few moments it will feel as if you're getting decimated. All you'll be doing is Arising, dying, Arising, dying...but be smart. You know when you need to run - or switch in the other party. Usually I actually caught a break and managed to get back on track. Be patient - don't interrupt the flow by doing something different from your pattern. Don't for example interrupt things by Berserking your tank or shooting a Hastega. It can be fatal.
Now - if you have to run - run all the way. Don't slink out of his range and chill because the dink WILL heal himself completely in only a few moments. Go all the way to the save crystal and take care of business. When you go back - Dispel, Expose, Watch for Cyclone, Dispelga yourself after he casts Reflectga on you. MAKE SURE your Dispelga has EVERYONE in range.
A halfway smart idea is to set up your B-Team the same as your A-Team gambit wise. Still - if things have gone so far wrong that all you have is your B-Team use them to run like hell for the save crystal. DO NOT TRY to get out of his range and have the B-Team "Arise" your KO'ed A-Team. I did this once and when I went back to the battle Yiazmat had full bars and full health. "Quit and return to the title screen"? You bet. But I lost two hours of battle time having to start from my last save. Don't get cocky - if you have to go: go!
If your ranged leader hiding on the stairs gets nailed - pick a new leader and when she (or he) gets Arisen - switch back to them immediately and stick them back on the stairs.
In this battle - the most important things to watch are the upper left corner of the screen (Cyclone), your MP (be ready to Syphon often) and status of tank. In the first 8/10 of the battle you will be using Gold Needles and Chrono Tears A LOT. Try NOT to take manual control of Decoy and Reverse - your people know their gambits and you'll just waste a turn.
If I did it - anyone can. YOU can. There is no magic bullet to this battle - I didn't use Dark Matter or summon Zodiark or any of that stuff. Besides the arcane magick I used it was pretty straightforward.
And finally - always remember to switch back to your original armor after the Windbreakers ...
If you can catch me - the experience is worth it!