Genkai 5 is going to be your final limit break. It will allow you to level past 70 to 75. The quest can be initiated with Maat in Ru'lude Gardens from level 66-70. He will initiated the quest Shattering Stars and ask you to bring a summoner testimony.

The overview: In my guide suggestion, for this fight you will Astral Flow x2. Hopefully if there is no resist, 2 astral will take him out. I think this method is best because Maat with smn/mnk sub is extremely fast and can do some major damage quick. Killing him fast, thereotically, would seem like the better method.

Summoner's Testimony (Rare/Ex) This papyrus scrolls reads: "The bearer of this document has proven excellence in the ways of the summoner." To obtain a summoner's testimony you must get it as a drop off of one of the follow mobs:

Tonberry Dismayer (Temple of Uggalepih) (Level: 61-67)
Abyssal Demon (Castle Zvahl Baileys) (Level: 64-66)
Tonberry Beleaguerer (Den of Rancor) (Level: 66-69)
Yagudo Avatar (Altar Room) (Level: 75)
Tzee Xicu the Manifest (Castle Oztroja) (Level: 85)

Again, like with any Rare/Ex item you may kill 5 to get the drop or you may kill 30. There is rumor moon phase may influece the drop but it's anyone's guess. You can only hold one testimony at a time in your inventory.

This video will cover what I'm going to talk about doing in the battle section. This person and I went in with basically the same strategy. I didn't create this video by the way, I'm just post a link to it:

Summoner Maat Video

For this fight you will need Hi-Ether and Refresh drinks. I took in two Hi-Potions but never needed them. I didn't even bother with food like pies for MP or crab for defense, etc. You're only concern is having enough MP to last the fight. Minimally, you can do the fight with a yagudo drink and 2 Hi-Ethers. I took two yagudo drinks and 4 Hi-Ether in.

Once you have the Summoner's Testimony in hand you may take it to Maat to initiate the fight. Supposedly, he will match the lowered stats of the crappy equipment. I have no confirmation on that, but some people swear by it. His level will be equal to yours. Also, you will get no subjob for the fight and he will be a smn/mnk.

Equip your crappy armor now. Trade the Summoner's Testimony and choose the battle option. He will warp you to Balga's Dais. Now walk from the burning circle you are at up to the next burning circle and trade summoner's testimony again. Now, this will warp you to the fight area. Maat will not attack you until you assault him, so don't worry about being attacked. Now its time to:

1. Put on your good armor.
2. Cast Light Spirit. Wait on Light Spirit to Protect IV and Shell IV.
3. Stoneskin and Blink afterwards.
4. Rest MP if needed. Use any food that you want.

Now, you are ready to run up to Maat and assault for the fight. I used Titan as my avatar for the added +VIT. Vitality lowers the damage curve and reduces the max amount of damage taken.

1. Cast avatar.
2. Refresh drink + Astral Flow.
3. Assault Maat.
4. After Titan hits Maat, use Earthen Fury or other special attack for other avatar. Do no move while Earthen Fury is being readied.
5. After it lands Run away! Pull back a bit and get ready to pop 2x Hi-Ethers.

Now here is something to note. Titan will probably hold out a bit, then Maat will do some attack on him that will kill him fast. Once Titan is dead, Maat will move back to you incredibily fast!

1 . As soon as you get off him a bit, pop 2x Hi-Ethers.
2. Watch for Titan to die and be ready to recast as soon as possible. As soon as Titan died, I cast but still Maat got to me and got a couple hits in on me. This will be the only tricky part.
3. Titan will assault Maat and once he's hitting him again, do another Earthen Fury. Or whatever special attack you are using with the avatar you use.
4. If Earthen Fury hits that second time, he should ideally die at this point.

Congratulations, two astral flow and maat is a owned. If for some reason that doesn't do it pop the next two Hi-Ethers and repeat the process. When he has been defeated you will obtain a Warp Scroll to warp back from East Sarta, where you end up.