[Deathblob]

Foodstamp is right, the following unit types will not be affected by Miasma:
Cold-blooded
Swamp Survival

And the following units are immune to disease (and hence Miasma):
Lifeless
Undead
Demons

Golems are not really a great plan against MA C'tis because he has cheap S1 shamans who will magic duel you. If you have access to Gift of Reason, Gargoyles are probably your cheapest E option for trashing his PD. C'tis PD is absolutely terrible. A Siege Golem eliminates the need for a big army to take down his walls.

To convert his dominion, your master smiths can make stone idols, or you can just sacrifice (you'll lose some to miasma) a few of your recruit-anywhere inquisitor black priests. I'd go with the priests, to save your gems.