Blacephalon/Naganadel was a Pokémon Trading Card Gamedeck archetype played in the 2018-2019 season. The deck's strategy revolved around accelerating Energy in the board to quickly deal knockouts with the deck's attackers. Blacephalon/Naganadel players ranked 2nd place in the Masters Division at the 2019 Pokémon Trading Card Game World Championships. Semifinalist Shintaro Ito's version was printed as a promotional World Championships deck, Mind Blown.
Strategy
Blacephalon/Naganadel focused on playing Blacephalon-GX's Mind BlownAttack to put Energy cards from the player's Pokémon into the Lost Zone and deal 50 damage times the number of cards sent this way, which in the right conditons could knock out any Pokémon in one hit. The attack required around 3 to 6 Energy to Knock Out most of the popular Pokémon in the format in one turn, but the deck played multiple Naganadel due to its Ability to recover Energy cards from the discard pile, as well as Beast Ring and later Welder as supporting Trainer cards to better set up more Energy cards on the board.
Naganadel itself could act as a secondary attacker that awarded only one Prize Card when Knocked Out, dealing more damage if the player had exactly 3 Prize Cards remaining. The deck later added Heatran-GX and Naganadel-GX as other backup attackers. Since cards in the Lost Zone could not be retrieved, the deck had plenty of extra Energy cards to make up for it.
Blacephalon-GX - For two Energy, Mind Blown lets the player put cards from their Pokémon in play (incuding Blacephalon-GX) to the Lost Zone and deal 50 damage times the number of cards sent this way. While Mind Blown could often not be able to Knock Out a Pokémon in the first turn, its other attacks that required only one Energy and would be usually played first; Bursting Burn burns and confuses the defending Pokémon while Burst-GX, only usable once per game, discards the player's prize card and attached it to one of their Pokémon if it was a Energy card.
Naganadel - Its Ability, usable once per turn, attaches a Basic Energy card from the discard pile to itself, easing the continuous use of Blacephalon-GX's Mind Blown. Turning Point also deals 80 damage plus 80 if the player has exactly 3 Prize Cards remaining. As a Pokémon with 130HP, Naganadel could survive certain attacks from popular decks, though its corresponding Basic stage, Poipole could be easily Knocked Out.
Naganadel-GX - As the deck already plays Poipole, it is easy to include this Pokémon into the deck. Its Ability allows the player to discard an Ultra Beast card from the player's hand to draw 3 cards once per turn. For 4 Energy, Venom Shoot deals 170 damage to any of the opponent's Pokémon; enough to Knock Out, for example, Benched Tapu Lele-GX. This attack requires a Energy, but it can be paid with Beast Energy ♢ or a single copy of Basic Energy in some versions of this deck.
Heatran-GX - When becoming the Active Pokémon during the player's turn, Burning Road can move any number of Energy from the player's other Pokémon to Heatran-GX. It serves as a secondary attacker with sightly more HP than Blacephalon-GX and can, once per game, attack the defending Pokémon with Hot Burn-GX for 50 times the amount of Energy attached to itself.
Welder - Attaches up to 2 Energy cards from the players' hand to a Pokémon in play and then allows the player to draw 3 cards. It can be used to power up all attackers in the deck.
Mysterious Treasure - Can be used to search the deck for the Naganadel line and other Pokémon by discarding another card, commonly a Energy to be brought back by Naganadel's Ability later.
Heat Factory ♢ - Stadium that allows the player to discard a Energy card from their hand once during their turn to draw cards. The lists would also use Ultra Space and Giant Hearth along this card.
Typical decklist
Zach Lesage's decklist at the 2019 Coinsville Regionals, USA
The following cards are often used in Blacephalon/Naganadel in place of certain cards included in the above lists.
Reshiram & Charizard-GX - Secondary attacker with more health than Blacephalon-GX, though it gives up one more Prize Card when Knocked Out.
Blacephalon - Secondary single-Prize attacker for lists that also use Energy.
Alolan Muk - Played before Heatran-GX was released to shut down Abilities from Basic Pokémon; lists with this card would play Ditto ♢ to make it easier to be put into play.
Energy cards from the player's Pokémon into the Lost Zone and deal 50 damage times the number of cards sent this way, which in the right conditons could knock out any Pokémon in one hit. The attack required around 3 to 6 Energy to Knock Out most of the popular Pokémon in the format in one turn, but the deck played multiple Naganadel due to its Ability to recover Energy cards from the discard pile, as well as Beast Ring and later Welder as supporting Trainer cards to better set up more Energy cards on the board.
Energy, but it can be paid with Beast Energy ♢ or a single copy of Basic 
