[Juzza]

You need to edit the pretender and add "#restrictedgod 95" or whatever nation you want to restrict the god to. There are lists of unit numbers in several places on the forums or you can select units in game by holding Shift and I dominions then then displays some information including their unit numbers.

This is what editing the Freak Lord would look like.

#selectmonster 246
#restrictedgod 95
#end

Answers to small questions like this can also be found in the modding.pdf in the docs folder of Dominions 3.