Butterspy

The Butterspy archetype runs on a self-sustaining Special Summon chain that keeps the hand stocked with bodies on the field without spending Normal Summons recklessly. Blue Mountain Butterspy triggers whenever a Warrior is Normal Summoned, dropping itself from the hand for free, while Moonlit Papillon replaces itself from the Deck the moment it leaves the field, ensuring the graveyard feeds back into a fresh presence on board. This recycling loop means the deck rarely runs dry of material mid-turn.

The primary payoff for flooding the board is Photon Alexandra Queen, an Xyz Monster requiring two Level 4 Butterspy monsters as material. Its detach effect bounces every monster on the field back to the hand and then deals 300 damage per card returned to each player's hand. Because the opponent typically controls fewer monsters than the Butterspy player does, the damage imbalance tilts in the deck's favour, and the bounce clears the field for an open attack. Swallowtail Butterspy compounds this pressure by stripping ATK from an opponent's monster equal to the battle damage another monster has already inflicted that turn, making it easier to run through anything that survived the bounce.

Morpho Butterspy and Butterspy Protection round out the aggressive gameplan by punishing position changes and offering reactive defence respectively. The deck naturally favours going second, since having a populated opponent's field gives Photon Alexandra Queen's bounce more targets and inflicts greater damage on the return.