So, for a card such as Way of the Crab that states:

"Action: Sacrifice a (friendly) CRAB character. Choose an opponent - that player must sacrifice a character. (Max 1 per round)."

When sacrificing the friendly, can that unit be face up in a province and/or in your conflict hand?

Characters on province are not in play, must choose a played character.

2 hours ago, Bayusi Haryon said:

Characters on province are not in play, must choose a played character.

Cheers!

Would a unit you use Blackmail on be considered friendly?

12 minutes ago, muzouka said:

Would a unit you use Blackmail on be considered friendly?

Yes, any unit you control is friendly. Even if that control is temporary.

You'd need to be playing Crab splash Scorpion agains a fellow Crab tho.

Many of the other Crab sacrifices don't require in to be a Crab character, just a friendly character however. So The combo would be better pulled off with Steadfast Witch Hunter, Stoic Gunso, or Funeral Pyre. This makes it useable against all clans.