one piece booster box op09 OP-09 Japanese Emperors of the New World The New Four Emperors Take the Helm in the 9th Pack One Piece Booster Box OP09

Essentially, it's a Negate Attack for Harpies that also stops a Monster effect

You cannot Special Summon monsters from the Extra Deck, except Fusion Monsters, the turn you activate either of this card's effects (even if this card leaves the field)

The flip side of this is using your sideboard to swap in cards you know your opponent cant deal with

Since 1000 Life Points can be regained relatively quickly, the drawback is well worth the benefit, and cards like Bad Reaction to Simochi and Darklord Nurse Reficule can be used in conjunction with Upstart Goblin, so the opponent loses 1000 Life Points instead, without inflicting any harm to you

Be on the lookout for a more technical breakdown from Ben Smith, one of our senior engineers, soon!

Legacy Death and Taxes decks have been employing similar packages as well