i went offensive/support and took warmaster.

build/gear kind of depends on the rest of your team comp since he's quishy. i have him built a few different ways, with toxic probably being my favorite but that one is used in a team with very good support champs.

regen/immortal is another option with high HP and resistance.  still 100%cr for a bit of damage, but it's purely a surviveability build to deal with the blue head.

lots of people probably go for a straight up damage build as he can lay the heat if set up properly, so that's another one to consider.

Did you get Lydia yet? If so, the best option is probably to gear him for damage and have him be on the same team as Lydia. The two combo very well.

I dont have lydia yet.  Expected to use duchess, duchess, pythion and build teams around them.  

You gave me a team but faster than i can build it i get new champs.  

Without Lydia, Shamael's utility is significantly reduced. He's still got value, since he hard-counters Torment, but then again so do both of your Duchesses.

I guess put him on the team with Pythion, and just build him as a nuker.

Which gear and stats will I need?