I don't know if you still wanted to know about Dark Wyrms but I did some research in Exile III. I found some wyrms and trapped them behind barriers. They didn't use a breath weapon but they did summon ghasts to attack me. You can also see that the breath weapon for the drake lord is listed under it's ability which suggests exile 3 doesn't have a dedicated spot for breath weapons. The dark wyrm's ability is paralysis touch. Pics for evidence: I got mad saves in exile 3 if you need to know anything else.