[Ewierl]

Using Gift of Reason to turn them into equippable commanders is indeed the standard practice. Their base cose is cheap (10 gems each, I believe?), so they're still an okay buy even when you are only getting full mileage out of those without Feebleminds and with Gift of Reason. Once equipped, they're probably the best non-unique SC chassis you can get (aside from the Seraph).

I seem to recall that you could randomly summon a commander Tartarian sometimes in Dom2, but I haven't used the spell much in Dom3.