[Baalz]

Demonbred are very, very good, but I have to say warlocks are one of my favorite mages of any nation. I generally recruit a few demonbred here and there for specific roles but primarily crank warlocks nonstop from my capital. Put a lab where they're bloodhunting and any of them can easily contribute forgings/rituals as needed while bloodhunting by default rather than researching. Here's what I see with the different random warlocks:

Blood - These are some of the best blood hunters in the game. With a sanguine rod these guys are pulling in 3-5 more blood slaves apiece vs a b1 hunter with a rod which is quite significant (say, a "free" hoard from hell per turn once you've set up a few bloodhunting provinces). Stick a blood booster on them and you've not only upped the blood output again, you've equipped a battery of disease demon spammers. You're also dropping ritual of the five gates and hoard from hell (stockpile your blood slaves over a few turns then swap the blood boosters over to non-B random warlocks to drop 10 or so in a round for a ridiculously effective *side* strategy to whatever else you were doing). Starshine caps and you've got a bunch of teleporting blood rain/bloodletting casters.

Astral - second best horror spam in the game (after Hinnom), easy gateways for those map move 1 troops, and teleporting support before you hit const-6 for those early elephant aggressors.

Earth - Bloodstones baby! And demon knights. Bloodstone + earth boots + crystal shield + earthpower = E5. Slap a starshine cap on for teleporting heavy earth support which is *oh* so tasty for Abysian heavy infantry.

Fire - well, these guys are probably inferior to the demonbred, but they do bring some nice niche uses to the table. Teleporting banish to inferno, soul contracts, and astral fires are all solid in their own niche.

After you hit const-6 the old age thing isn't an issue, it's trivial to slap boots of youth on your one per turn warlock recruitment.

All in all, demonbred is not who I think of when I think versatility and MA Abysia. I also think it's a very good idea to stick labs under your warlock bloodhunters and use them as heavy lab mages as well as bloodhunters, something you can't do with scout bloodslave-shuttles. It's really nice to be able to drop 15 lesser horrors/disease demons/hoard from hells on a turn's notice.