Blacksad
Explorer
I don't think D20 needs to be modified too much to work for discworld.
As said in the GURPS book, you shouldn't use system with high hit points, as it remove the fear of death, for this you could use the grim & gritty hit point and combat rules from: http://www.sleepingimperium.rpghost.com/
It recreate perfectly the fear that discworl heroes have from a fireball or falling from a cliff or an angry troll.
For the mages, the magic system is similar to the standard wizard, with probably the removal of the summon familiar ability (make it a feat), and a use/creat rod ability instead (using rules from the psi srd/handbook for crystal capacitor or something like that).
I don't know how the witch magic work, but waiting for the return of the witch and warlock netbook at the fantasy community council might help a lot here.
As said in the GURPS book, you shouldn't use system with high hit points, as it remove the fear of death, for this you could use the grim & gritty hit point and combat rules from: http://www.sleepingimperium.rpghost.com/
It recreate perfectly the fear that discworl heroes have from a fireball or falling from a cliff or an angry troll.
For the mages, the magic system is similar to the standard wizard, with probably the removal of the summon familiar ability (make it a feat), and a use/creat rod ability instead (using rules from the psi srd/handbook for crystal capacitor or something like that).
I don't know how the witch magic work, but waiting for the return of the witch and warlock netbook at the fantasy community council might help a lot here.