Greater Whirlwind attacks help a lot. Somehow my party won that battle without magic. We just managed to survive long enough to wait until all his defence went down and then a couple of Whirlwinds did the trick. It would be nice to use magic, of course, but the second thing Draconis did in his dragon form after surrounding himself with all those defences was killing Edwin. Finally I had to keep Edwin away from the fight - otherwise he couldn't survive.
And for my second playthrough it was completely different fight - with Ruby Ray and Abi Dahlsim Horrid whilting... I still wonder WHY Draconis kept killing Edwin all the time in the first battle, and did not do the same clever thing in the second.
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Tanda,
with best regards from Guild of Assassins