Properly played, "Harpies" can overwhelm the opponent in moments with high attack power and powerful effects, but they are not strong individually, so they are vulnerable to opponents who can overpower them, or destroy all of them at once
You spent four Black mana and drew 7 cards for 7 life
First, there's a new mechanic called Sneak, which is a riff on the pre-existing Ninjutsu, in which players can cheat big creatures onto the battlefield whenever an attacking creature goes unblocked
The new set features 20 of these doubled lands/spells, and I love them so much Ive upended one of my cubes (a hand-selected collection of draftable cards) to accommodate them
Ask anyone what comes to mind first when they think of Ixalan, and 90% of them will tell you one of the creature factions (the other 10% will say Colossal Dreadmaw)