I was able to beat Maat on the first try.
Here is what I did:
I waited until Firesday because the two most powerful acient magic is Flare and Flood. On Firesday, Flare would be strong. Since Fire is weak to Water, Flood would also be strong. So going on Firesday, Flare and Flood would have a higher chance of landing for full damage.
When you get to the BC, eat your pie (I ate Melon +1). Once I got into the BC I drank a Yagudo drink.
Just get close enough to Maat so you can cast on him. Here's the spell/ability order:
1. First cast Flare.
2. Elemental Seal + Sleep II (I like Sleep II over Sleepga II because of its faster cast time).
3. Manfont.
4. Flood.
5. Thunder III
I didn't even get scratched. I had macro's set up for the above actions, and just hit alt-1,2,3,4,5 in turn.
Good luck.