Reversal Box

Once per turn, during the Standby Phase: Roll a six-sided die, and place counters on this card (max. 6), up to the result. When a monster effect is activated on your opponent's field, or once per battle, during damage calculation, if your opponent's monster attacks: You can remove 1 counter from this card, then target 1 of those monsters; toss a coin and call it. If you call it right, Special Summon 1 monster that mentions "Dark Time Wizard" from your Deck, and if you do, until the end of this turn, change the targeted monster's ATK to 0, also negate its effects.