Committed Hero said:
The bulk of the work would be converting spell slots/magic energy into Art scores. Figuring out the cleric's role would be the most challenging thing.
I LOVE Ars Magica, 4th edition, but i've never had the pleasure to acutally play it. Picked up the pdf a while back and just his past weekend I sat down to convert it to d20. Now, there is a fella who has already done this (
http://www.users.qwest.net/~jordanerik/Gaming/index.htm)
but I wanted a crack at it. I simply took the Magnitude Ratings (5,10,15 etc) and said they were DC's. DC 5 is basically a cantrip. DC 15-20 is roughly a 3rd level spell. If you compare the spells in Ars Magica to DnD spells that do the same thing (such as a fireblast) you'll find that the level and Magnitude are about the same. It made the conversion process a whole lot easier.
Then i figured that all magi get magic skill points at 4+INT mod x 4, then 4+mod/level, just like regular Dnd. Every spellcaster automatically has the 5 Techniques at beginning of play: I Control, I Destroy, I Transform, I Create, I Perceive. You can't have more than 3 + your level in ranks, as per d20. Then you have the 10 Forms to choose from. This part offers tons of flexibilty in building a character. As a 1st level character you might have access to 5 of the forms, and pick up new ones later.
So you add skill ranks to Technique, and skill ranks to Form. Then, you average them together for your final roll.
Eh, there's more, but I won't go into it. Not in this thread anyway.
Oh, and Arcana Evolved has a fantastic magic system. And Conan d20 has oodles of flavor, but it's a little too wanky to use.