Okay, thanks (again).
It´s a bit irritating, that nearly all attacks talking about "harpies" (plural) or flock. And the Mass Attack! of "Each attack ..."
So just to get it right: If I have three harpies, they get one card and then the GM roles or chooses three different attacks with the damage for a single harpy (e.g. Coordinated Attack! (2D6), Mass Attack! (D8) and Death from Above! (D6)).
I take it that each Harpy gets its own init card:
<> and each harpy gets a turn per round <>
But on each of those turns they perform a group attacks:
<> with each attack consuming a turn for one harpy.
But if the GM so chooses, he can group all the harpies under one card, just as with NPCs. But since if the PCs are fighting harpies, they rarely fight anything else, so why not give all the harpies their init card, to spread out the menace in the round.
So technically it works like one monster, but with the difference that each harpy have their own HP and turn (during they always attack as a group) and if a single harpy dies, the group has one less turn and if half of them dies, the rest flees.