Which Skill to rank 3:

Sean0333

I'm looking to rank 3 a 7 star skill. I still have to do the necropolis if that helps to decide. The 7 stars I have that are skill are hit-monkey, attuma, moondragon, korg, and comic black panther

KCOF

If you want pure offensive power, go Hit-Monkey (Though he's a little too squishy imo even at R3) or OG Black Panther (if you don't mind having to do intercepts to access his full damage potential).

But if you don't mind champs that need to ramp, either Attuma (Attuma is more of a defense pick and almost needs the awakening to be viable for both defense and offense) or Moondragon (kind of a similar case to OG Black Panther, but is a little less stressful to play).

Unfortunately, none of your picks are really super viable for Necropolis runs except for maybe Moondragon since her reverse controls immunity is quite clutch for the Grandmaster.

Sorry if I'm a little too on the fence on my answer, but It's really up to your preferences (such as whether you like fast-ramp-up champs or have a taste for build-up champs).