My recollection with Black Magic was that the asker would point at random things and the guesser would say now and then the asker would point at something black and that was the hint to the guesser that whatever was pointed at next would be the secret object.
A similar game that I remember driving people to distraction with was Johnny Johnny Whoop. You’d tap the fingers of one hand with the index finger of the other hand starting from the pinky and moving toward the thumb, saying Johnny with each tap and sliding your finger down the index finger to the thumb saying “Whoop”. “Johnny, Johnny, Johnny, Johnny, Whoop, Johnny, Whoop, Johnny, Johnny, Johnny, Johnny”. And at the end of the sequence, touch your hair or scratch your ear or fold your arms or whatever pre-determined signal you come up with that doesn’t look like part of the sequence. Other kids are challenged to repeat what you did and if they don’t end with your same secret sign, they did it wrong.