Being a firm believer that Forgeworld rules should be used I've okayed them for the campaign I'm running and am pushing to make them usable in local tournaments including one of the larger ones in our tri-state area. It unlocks so many more models and potential for armies not only in games but in customization. So I decided to add Armenneus Valthex to my army instead of a normal chapter master. He is a special character created for the Astral Claws pre-chaos and he is listed as a HQ choice in Badab War p1 for Codex: Space Marines. In fact if you want more HQ options for a vanilla marine army get that book. Also has some options for blood angels. (lamentor's chapter)
So why Valthax. Well, I wanted to field a Master of the Forge with a conversion beamer sit back in my deployment. The MotF's major job would be firing the conversion beamer and repairing the Predator Executioner and Hellfire Dreadnought (las/missile combo dread) while staying in cover behind the Aegis defense line. A normal MotF with power weapon and beamer is 145, where Valthex is 145 and is a lot more efficient. For starters the Battle Alchemistry special rules gives him and a chosen squad hellfire rounds that have poison (2+). Second his Indynabula Array give him a 5+ invulnerable. An invulnerable save is something tech marines and MotF should have had anyways so this makes me happy. He can re-roll his blessing of the Omnissiah allowing a higher chance of vehicle repairs. Then lastly his Indynabula Array counts as having a pair of power weapons giving him 3 total attacks which isn't a lot but more then he would get normally.
So for the points cost he's an excellent support troop. Giving several bonus's over normal Masters of the Forge. His only downside is he still has a normal state line so isn't any stronger then normal marines, just better armed.