5th at Regional Monterrey, Junior Division
8th at Regional Pittsburgh, Junior Division
26th at Philippines Premier Ball League
Crustle is the definition of a "matchup fish", as the video game side of the Pokémon community calls it. Most of its matchups are one-sided; either Crustle will stomp the opposing deck easily unless it bricks (which happens more often that you might think, considering it has no Bench-sitters with draw/search Abilities and has to rely solely on Supporters), or the opposing deck will stomp Crustle easily unless they brick.
Among the top tier decks, Gardevoir ex is a very bad matchup for Crustle, as it can attack with Scream Tail, Drifloon, or even Mew ex, and has its own Munkidoris to send damage back (or to Confuse Crustle if it doesn't have Mist Energy!). This is the main gatekeeper that prevents Crustle from being further up; Gardevoir ex is always popular and you'll likely run into it at some point. Further down the tier list, Ethan's Typhlosion is almost unbeatable for Crustle. On the other hand, Crustle has very favorable matchups against Gholdengo ex, N's Zoroark ex, and Flareon ex.
Get Dwebble into the Active Spot and use Ascension to evolve it into Crustle. If you don't start Crustle, Arven for Buddy-Buddy Poffin/Nest Ball + Air Balloon or Colress's Tenacity for Artazon + Jet Energy can search it out and maneuver it into the Active Spot. Once Crustle is down, its protective Ability should buy you time to set up the rest of your board, getting Munkidori into play and attaching Energy to them (and Crustle itself) with Technical Machine: Turbo Energize or Crispin.
After you're set up, if your opponent still doesn't have an answer to Crustle, you should be able to win by slowly spamming Superb Scissors. If your opponent does have an answer, you'll want to Boss it up and eliminate it, which is why the deck runs 4 copies.
This deck has only two possible attackers: Crustle or Cornerstone Mask Ogerpon ex. Their attacks are honestly unimpressive; it's their protection Abilities that make them what they are. These Abilities already shut off a large number of attackers, and the remaining gaps in the armor are plugged by:
Munkidori and Poké Vital A healing
Mist Energy preventing Roaring Moon ex's instant KO attack, Sylveon ex shuffling it back into the deck after Bossing something else out, or Munkidori's Confusion
Luxurious Cape giving Crustle +100 HP to survive random non-ex Fire-type attacks (e.g. Charmeleon, Armarouge)
This deck wants to go second, as it wants to attack with a Basic Pokémon (Dwebble) AND play Supporters as soon as possible. Going second also denies your opponent a possible Fan Rotom donk if you start only Dwebble.
Poké Vital A. The outs that most decks have against Crustle do 150 or less damage, so Poké Vital A basically blanks one attack.
Iron Thorns ex + Future Booster Energy Capsule + Lightning Energy: Alternative attacker that tries to put the screws on your opponent by shutting off their ex Abilities instead of walling. Most of the meta decks have draw or Energy acceleration Abilities on their ex's. Iron Thorns ex can also trap Latias ex after you Boss it up.
3-3 N's Zoroark ex + 1 N's Reshiram: This variant attempts to fix the Gardevoir ex weakness by including an alternative attacker that can 1HKO it, which doubles as a draw engine in other matchups. However, N's Zoroark ex can become a 2-Prize liability.
Super Potion: Additional healing.
Lana's Aid: Recovery card. Useful for picking up Munkidori/Crustle and their attached Energy after a KO.
Technical Machine: Blindside: This lets you snipe non-ex Bench sitters. Use Adrena-Brain to move damage onto the target.
Reversal Energy: A quick way to power up Crustle if you're behind in Prizes.
If you need to attach Technical Machine: Turbo Energize to Crustle, do so before attaching Luxurious Cape, since you can't have 2 Tools attached at once (and Luxurious Cape won't bin itself).
Mew ex is seen in a good number of decks, and can damage Crustle or Cornerstone Mask Ogerpon ex by copying their attacks.
Dusknoir from Dragapult ex can KO Crustle by using Neo Upper Energy to power its attack, and Jamming Tower to blank Luxurious Cape.