Hundred Dragon (Prismatic Secret Rare)

Once per turn, during your Main Phase: You can activate this effect; until the end of this turn, increase this card's Level by the number of cards you control, and if you do, this card gains ATK equal to the Level increase x 100. If this card is sent to the GY: You can target 1 face-up monster you control that was Special Summoned from the Extra Deck; the first time that face-up monster would be destroyed by battle or card effect, it is not destroyed. You can only use this effect of Hundred Dragon once per turn.