AbilityShadow Hunt
This Pokémon can use the attacks of Basic Pokémon in your discard pile. (You still need the necessary Energy to use each attack.)

Marshadow is Pokédex #802, generation 7 (Alola). Marshadow-GX is a Basic GX Fighting Pokémon with 150 HP.
Marshadow-GX sits at SM59/248 in SM Black Star Promos, position 60 of 251. Before it is SM58 Necrozma-GX, and after it is SM60 Charizard-GX. The set belongs to the Sun & Moon series. It was released on 3 February 2017. The printed size is 248. This checklist is longer, at 251 cards. The listed rarity is Promo.
Shadow Hunt is listed as Ability. This Pokémon can use the attacks of Basic Pokémon in your discard pile. (You still need the necessary Energy to use each attack.) The attack Beatdown lists 120 damage. The cost is Fighting, Fighting, Colorless. Peerless Hundred Blows-GX is another attack lists 50× damage. The cost is Fighting. This attack does 50 damage times the number of basic Energy attached to this Pokémon. (You can't use more than 1 GX attack in a game.) Weakness is Psychic ×2. Retreat cost is 1. The card text says: Pokémon-GX rule: When your Pokémon-GX is Knocked Out, your opponent takes 2 Prize cards.
Marshadow (#802) has 16 other cards in the catalog. Those other cards are in 8 sets. The other printings with a release date run from 2017 to 2026. The earliest other card is Marshadow SM85/248 in SM Black Star Promos (2017). That card is named Marshadow, while this one is Marshadow-GX. That card lists 70 HP, and this one lists 150 HP. Both list the rarity Promo. Emi Ando illustrated that card, and 5ban Graphics illustrated this one. 13 other cards of Marshadow list a different HP.
The illustrator line reads 5ban Graphics. I count 1,629 other cards in the catalog with that illustrator.
SM Black Star Promos set binder is where a full SM Black Star Promos set goes. This card fills one slot there. A generation binder holds one card of each species. Marshadow can fill a slot in Generation 7 binder (Alola). I still need this card.
This Pokémon can use the attacks of Basic Pokémon in your discard pile. (You still need the necessary Energy to use each attack.)
This attack does 50 damage times the number of basic Energy attached to this Pokémon. (You can't use more than 1 GX attack in a game.)
Pokémon-GX rule: When your Pokémon-GX is Knocked Out, your opponent takes 2 Prize cards.
SM Black Star Promos, in the Sun & Moon series. It was released on 3 February 2017. The printed size is 248.
SM59/248. It is entry 60 of 251 in this checklist.
5ban Graphics. The catalog lists 1,629 other cards with that illustrator.
Promo.
Marshadow #802, generation 7 (Alola).
Beatdown (120) and Peerless Hundred Blows-GX (50×).