Started to decode the monsters data & have done a lot of cartography/decoding of the code today, especially the combat system which is the biggest block of the game.
I also have aligned the monsters and heroes graphics on grids for easier display.
The FAQ i've read is mostly wrong about the monsters attributes (although it was valuable to understand the maps even if they're from the rotated C64 version ;)) thanks must go to Andrew Schultz for that.
I also found a pdf manual of Phantasie I which apparently was the one included with the second opus too, i devised some infos from it as well(also it contains some interesting tips about the variations of the C64 version)
The combat system is a quite complex piece of spaghetti code and as soon as I've got it the rest should be a walk in the park (dungeons are using the same system, of course).
The music and sound of the ST version are using the stand DOSOUND XBIOS API (which seems to be described here) so maybe it'll be relatively easy to convert that to a friendlier format.