If you look at the body's those two have then you'll see that they don't have to be active to be activated during the game.
Now if you have 4 darkrai g/nidokings in play, would it increase the damage by 10/20 for each extra darkrai g/nidoking?
Now if you have 4 darkrai g/nidokings in play, would it increase the damage by 10/20 for each extra darkrai g/nidoking?