Fiend-Type monsters you control gain 500 ATK. You can target 1 "Archfiend" monster you control; banish 1 other Fiend-Type monster you control, and if you do, Special Summon from your hand, Deck, or Graveyard, 1 "Archfiend" monster with same Level as the targeted monster. You can only use this effect of "Archfiend Palabyrinth" once per turn.
Learn to read!
pretty sure he knows that.
I think he meant thatnu can only have this card once in your deck so you can only activate it once (if you dont use hidden spell book or sth else)