If this face-up card is destroyed while in a Monster Card Zone, you can place it face-up in your Spell & Trap Card Zone as a Continuous Spell Card, instead of sending it to the Graveyard. While this card is treated as a Continuous Spell Card by this effect, during each player's Standby Phase: Place 1 Pumpkin Counter on this card. All monsters your opponent controls lose 100 ATK and DEF for each Pumpkin Counter on this card.
I forgot to add that, even though it doesn't work on this cancer card. Stamping Destruction does which doesn't make any sense. They both say destroy a spell/trap card on your opponent's field. But with Exterio's Fang, the spell/Trap card has to activate which in pumpkin princess' case, she ACTIVATES her effect while being in the spell/trap card zone and can be destroyed by cards like