Ditto's Sudden Transformation can use Terrakion's Cavern Tackle every turn.

datamaru

Just fought someone that can use Cavern Tackle via Ditto to get immune from damage every turn without any repercussion. I'm pretty sure this is an illegal move by PTCG ruling. Please fix this. It's pretty annoying and game-breaking.

Here's the battle log:

Setup
Kaskaede chose heads for the opening coin flip.
Kaskaede won the coin toss.
Kaskaede decided to go second.
Kaskaede drew 7 cards for the opening hand.

• 7 drawn cards.
  datamaru drew 7 cards for the opening hand.
• 7 drawn cards.
  • Basic Fighting Energy, Earthen Vessel, Basic Grass Energy, Professor Sada's Vitality, PokéStop, Night Stretcher, Professor Sada's Vitality
  datamaru took a mulligan.
• Cards revealed from Mulligan 1
  • Basic Fighting Energy, Earthen Vessel, Basic Grass Energy, Professor Sada's Vitality, PokéStop, Night Stretcher, Professor Sada's Vitality
  Kaskaede drew 1 more card because datamaru took at least 1 mulligan.
• Kaskaede drew a card.
  Kaskaede played Radiant Greninja to the Active Spot.
  datamaru played Raging Bolt ex to the Active Spot.

Turn # 1 - datamaru's Turn
datamaru drew Basic Fighting Energy.
datamaru played Teal Mask Ogerpon ex to the Bench.
datamaru played Nest Ball.

• datamaru drew Teal Mask Ogerpon ex and played it to the Bench.
• datamaru shuffled their deck.
  datamaru played Nest Ball.
• datamaru drew Squawkabilly ex and played it to the Bench.
• datamaru shuffled their deck.
  datamaru played PokéStop to the Stadium spot.
  datamaru attached Basic Fighting Energy to Raging Bolt ex in the Active Spot.
  datamaru's Squawkabilly ex used Squawk and Seize.
• datamaru discarded 2 cards.
  • Canceling Cologne, Professor Sada's Vitality
• datamaru drew 6 cards.
  • Pokémon Catcher, Basic Lightning Energy, Basic Grass Energy, Teal Mask Ogerpon ex, Trekking Shoes, Switch Cart
  datamaru's Teal Mask Ogerpon ex used Teal Dance.
• datamaru attached Basic Grass Energy to Teal Mask Ogerpon ex on the Bench.
• datamaru drew Energy Retrieval.
  datamaru played Trekking Shoes.
• datamaru drew Basic Grass Energy.
  datamaru's Teal Mask Ogerpon ex used Teal Dance.
• datamaru attached Basic Grass Energy to Teal Mask Ogerpon ex on the Bench.
• datamaru drew Switch Cart.
  datamaru ended their turn.

Turn # 1 - Kaskaede's Turn
Kaskaede drew a card.
Kaskaede played Buddy-Buddy Poffin.

• Kaskaede drew 2 cards and played them to the Bench.
  • Ditto, Bidoof
• Kaskaede shuffled their deck.
  Kaskaede played Hisuian Heavy Ball.
• Kaskaede moved Kaskaede's Ting-Lu to their hand.
• Kaskaede moved Kaskaede's Hisuian Heavy Ball to the Prize cards.
• Kaskaede shuffled their Prize cards.
  Kaskaede played PokéStop.
• datamaru moved datamaru's 3 cards to the discard pile.
  • Arven, Energy Switch, Nest Ball
• datamaru moved datamaru's 2 cards to their hand.
  • Energy Switch, Nest Ball
  Kaskaede played Nest Ball.
• Kaskaede drew Squawkabilly ex and played it to the Bench.
• Kaskaede shuffled their deck.
  Kaskaede's Radiant Greninja used Concealed Cards.
• Kaskaede discarded Basic Fighting Energy.
• Kaskaede drew 2 cards.
  Kaskaede attached Basic Fighting Energy to Ditto on the Bench.
  Kaskaede played Collapsed Stadium to the Stadium spot.
• datamaru discarded PokéStop.
  Kaskaede played Iono.
• Kaskaede shuffled their hand.
• Kaskaede put 6 cards on the bottom of their deck.
• datamaru shuffled their hand.
• Kaskaede moved Kaskaede's 6 cards to their deck.
  • Teal Mask Ogerpon ex, Basic Lightning Energy, Energy Retrieval, Switch Cart, Switch Cart, Pokémon Catcher
• Kaskaede drew 6 cards.
• Kaskaede drew 6 cards.
  • Lost Vacuum, Pokégear 3.0, Raging Bolt ex, PokéStop, Raging Bolt ex, Earthen Vessel
  Kaskaede played Buddy-Buddy Poffin.
• Kaskaede shuffled their deck.
  Kaskaede played Buddy-Buddy Poffin.
• Kaskaede shuffled their deck.
  Kaskaede played Cornerstone Mask Ogerpon ex to the Bench.
  Kaskaede played Glass Trumpet.
• Kaskaede attached Basic Fighting Energy to Ditto on the Bench.
  Kaskaede's Squawkabilly ex used Squawk and Seize.
• Kaskaede discarded 2 cards.
  • Arven, Bibarel
• Kaskaede drew 6 cards.
  Kaskaede played Earthen Vessel.
• Kaskaede discarded Ting-Lu.
• Kaskaede drew 2 cards.
  • Basic Fighting Energy, Basic Fighting Energy
• Kaskaede shuffled their deck.
  Kaskaede ended their turn.

Turn # 2 - datamaru's Turn
datamaru drew Basic Fighting Energy.
datamaru played PokéStop to the Stadium spot.

• Kaskaede discarded Collapsed Stadium.
  datamaru played Earthen Vessel.
• datamaru discarded Raging Bolt ex.
• datamaru drew 2 cards.
  • Basic Grass Energy, Basic Lightning Energy
• datamaru shuffled their deck.
  datamaru played Raging Bolt ex to the Bench.
  datamaru's Teal Mask Ogerpon ex used Teal Dance.
• datamaru attached Basic Grass Energy to Teal Mask Ogerpon ex on the Bench.
• datamaru drew Professor Sada's Vitality.
  datamaru played PokéStop.
• datamaru moved datamaru's 3 cards to the discard pile.
  • Night Stretcher, Switch Cart, Raging Bolt ex
• datamaru moved datamaru's 2 cards to their hand.
  • Night Stretcher, Switch Cart
  datamaru played Pokégear 3.0.
• datamaru drew Boss's Orders.
• datamaru shuffled their deck.
  datamaru attached Basic Lightning Energy to Raging Bolt ex in the Active Spot.
  datamaru played Boss's Orders.
• Kaskaede's Cornerstone Mask Ogerpon ex was switched with Kaskaede's Radiant Greninja to become the Active Pokémon.
  Kaskaede's Cornerstone Mask Ogerpon ex is now in the Active Spot.
  datamaru's Raging Bolt ex used Bellowing Thunder on Kaskaede’s Cornerstone Mask Ogerpon ex for 210 damage.
• Basic Fighting Energy was discarded from datamaru's Raging Bolt ex.
• 2 cards were discarded from datamaru's Teal Mask Ogerpon ex.
  • Basic Grass Energy, Basic Grass Energy
  Kaskaede's Cornerstone Mask Ogerpon ex was Knocked Out!
  Kaskaede's Ditto is now in the Active Spot.
  datamaru took 2 Prize cards.
  Fezandipiti ex was added to datamaru's hand.
  Trekking Shoes was added to datamaru's hand.

Turn # 2 - Kaskaede's Turn
Kaskaede drew a card.
Kaskaede attached Basic Fighting Energy to Ditto in the Active Spot.
Kaskaede played Night Stretcher.

• Kaskaede moved Kaskaede's Bibarel to their hand.
  Kaskaede evolved Bidoof to Bibarel on the Bench.
  Kaskaede's Radiant Greninja used Concealed Cards.
• Kaskaede discarded Basic Fighting Energy.
• Kaskaede drew 2 cards.
  Kaskaede played PokéStop.
• datamaru moved datamaru's 3 cards to the discard pile.
  • Ultra Ball, Bidoof, Ultra Ball
• datamaru moved datamaru's 2 cards to their hand.
  • Ultra Ball, Ultra Ball
  Kaskaede played Ultra Ball.
• Kaskaede discarded 2 cards.
  • PokéStop, Ultra Ball
• Kaskaede drew Terrakion.
• Kaskaede shuffled their deck.
  Kaskaede played Earthen Vessel.
• Kaskaede discarded Terrakion.
• Kaskaede drew 2 cards.
  • Basic Fighting Energy, Basic Fighting Energy
• Kaskaede shuffled their deck.
  Kaskaede played Ultra Ball.
• Kaskaede discarded 2 cards.
  • Basic Fighting Energy, Ultra Ball
• Kaskaede drew Terrakion.
• Kaskaede shuffled their deck.
  Kaskaede's Bibarel used Industrious Incisors.
• Kaskaede drew a card.
  Kaskaede's Ditto used Cavern Tackle on datamaru’s Raging Bolt ex for 120 damage.

Turn # 3 - datamaru's Turn
datamaru drew Trekking Shoes.
datamaru played Trekking Shoes.

• datamaru drew Basic Grass Energy.
  datamaru's Teal Mask Ogerpon ex used Teal Dance.
• datamaru attached Basic Grass Energy to Teal Mask Ogerpon ex on the Bench.
• datamaru drew Superior Energy Retrieval.
  datamaru played Trekking Shoes.
• datamaru drew Radiant Greninja.
  datamaru played Radiant Greninja to the Bench.
  datamaru's Radiant Greninja used Concealed Cards.
• datamaru discarded Basic Fighting Energy.
• datamaru drew 2 cards.
  • Nest Ball, Night Stretcher
  datamaru played Professor Sada's Vitality.
• datamaru attached Basic Fighting Energy to Raging Bolt ex in the Active Spot.
• datamaru attached Basic Fighting Energy to Raging Bolt ex on the Bench.
• datamaru drew 3 cards.
  • Nest Ball, Earthen Vessel, Pokégear 3.0
  datamaru played Earthen Vessel.
• datamaru discarded Nest Ball.
• datamaru drew 2 cards.
  • Basic Lightning Energy, Basic Grass Energy
• datamaru shuffled their deck.
  datamaru's Teal Mask Ogerpon ex used Teal Dance.
• datamaru attached Basic Grass Energy to Teal Mask Ogerpon ex on the Bench.
• datamaru drew Professor Sada's Vitality.
  datamaru played PokéStop.
• datamaru moved datamaru's 3 cards to the discard pile.
  • Switch Cart, Professor Sada's Vitality, Iono
• datamaru moved datamaru's Switch Cart to their hand.
  datamaru played Switch Cart.
• datamaru's Raging Bolt ex was switched with datamaru's Raging Bolt ex to become the Active Pokémon.
• datamaru's Raging Bolt ex healed 30 damage.
  datamaru's Raging Bolt ex is now in the Active Spot.
  datamaru ended their turn.

Turn # 3 - Kaskaede's Turn
Kaskaede drew a card.
Kaskaede played Earthen Vessel.

• Kaskaede discarded Terrakion.
• Kaskaede shuffled their deck.
  Kaskaede's Radiant Greninja used Concealed Cards.
• Kaskaede discarded Basic Fighting Energy.
• Kaskaede drew 2 cards.
  Kaskaede played PokéStop.
• datamaru moved datamaru's 3 cards to the discard pile.
  • Iono, Energy Switch, Ditto
• datamaru moved datamaru's Energy Switch to their hand.
  Kaskaede's Ditto used Cavern Tackle on datamaru’s Raging Bolt ex for 120 damage.

Turn # 4 - datamaru's Turn
datamaru drew Pokégear 3.0.
datamaru's Radiant Greninja used Concealed Cards.

• datamaru discarded Basic Lightning Energy.
• datamaru drew 2 cards.
  • Pal Pad, Energy Retrieval
  datamaru played PokéStop.
• datamaru moved datamaru's 3 cards to the discard pile.
  • Prime Catcher, Pokémon Catcher, Earthen Vessel
• datamaru moved datamaru's 3 cards to their hand.
  • Prime Catcher, Pokémon Catcher, Earthen Vessel
  datamaru played Pal Pad.
• datamaru shuffled 2 cards into their deck.
  • Iono, Boss's Orders
  datamaru played Earthen Vessel.
• datamaru discarded Nest Ball.
• datamaru drew 2 cards.
  • Basic Lightning Energy, Basic Fighting Energy
• datamaru shuffled their deck.
  datamaru played Prime Catcher.
• Kaskaede's Squawkabilly ex was switched with Kaskaede's Ditto to become the Active Pokémon.
• datamaru's Raging Bolt ex was switched with datamaru's Raging Bolt ex to become the Active Pokémon.
  Kaskaede's Squawkabilly ex is now in the Active Spot.
  datamaru's Raging Bolt ex is now in the Active Spot.
  datamaru's Raging Bolt ex used Bellowing Thunder on Kaskaede’s Squawkabilly ex for 210 damage.
• 2 cards were discarded from datamaru's Raging Bolt ex.
  • Basic Lightning Energy, Basic Fighting Energy
• Basic Grass Energy was discarded from datamaru's Teal Mask Ogerpon ex.
  Kaskaede's Squawkabilly ex was Knocked Out!
  Kaskaede's Ditto is now in the Active Spot.
  datamaru took 2 Prize cards.
  Earthen Vessel was added to datamaru's hand.
  Slither Wing was added to datamaru's hand.

Turn # 4 - Kaskaede's Turn
Kaskaede drew a card.
Kaskaede's Ditto used Cavern Tackle on datamaru’s Raging Bolt ex for 120 damage.

Turn # 5 - datamaru's Turn
datamaru drew Teal Mask Ogerpon ex.
datamaru played Pokémon Catcher.

• datamaru flipped a coin and it landed on heads.
• Kaskaede's Bibarel was switched with Kaskaede's Ditto to become the Active Pokémon.
  Kaskaede's Bibarel is now in the Active Spot.
  datamaru played Professor Sada's Vitality.
• datamaru attached Basic Lightning Energy to Raging Bolt ex in the Active Spot.
• datamaru attached Basic Lightning Energy to Raging Bolt ex on the Bench.
• datamaru drew 3 cards.
  • Pokémon Catcher, Pokémon Catcher, Iono
  datamaru attached Basic Fighting Energy to Raging Bolt ex in the Active Spot.
  datamaru's Raging Bolt ex used Bellowing Thunder on Kaskaede’s Bibarel for 140 damage.
• 2 cards were discarded from datamaru's Raging Bolt ex.
  • Basic Lightning Energy, Basic Fighting Energy
  Kaskaede's Bibarel was Knocked Out!
  Bidoof was discarded from Kaskaede's Bibarel.
  Kaskaede's Ditto is now in the Active Spot.
  datamaru took a Prize card.
  Basic Grass Energy was added to datamaru's hand.

Turn # 5 - Kaskaede's Turn
Kaskaede drew a card.
Kaskaede played PokéStop.

• datamaru moved datamaru's 3 cards to the discard pile.
  • Ditto, Penny, Night Stretcher
• datamaru moved datamaru's Night Stretcher to their hand.
  Kaskaede played Pal Pad.
• Kaskaede shuffled Penny into their deck.
  Kaskaede played Brilliant Blender.
• Kaskaede moved Kaskaede's 4 cards to the discard pile.
  • Bloodmoon Ursaluna, Cornerstone Mask Ogerpon ex, Ditto, Nest Ball
• Kaskaede shuffled their deck.
  Kaskaede played Night Stretcher.
• Kaskaede moved Kaskaede's Basic Fighting Energy to their hand.
  Kaskaede's Radiant Greninja used Concealed Cards.
• Kaskaede discarded Basic Fighting Energy.
• Kaskaede drew 2 cards.
  Kaskaede played Penny.
• Kaskaede moved Kaskaede's Radiant Greninja to their hand.
  Kaskaede's Ditto used Cavern Tackle on datamaru’s Raging Bolt ex for 120 damage.
  datamaru's Raging Bolt ex was Knocked Out!
  datamaru's Radiant Greninja is now in the Active Spot.
  Kaskaede took 2 Prize cards.
  A card was added to Kaskaede's hand.
  A card was added to Kaskaede's hand.

Turn # 6 - datamaru's Turn
datamaru drew Briar.
datamaru played Slither Wing to the Bench.
datamaru ended their turn.

Turn # 6 - Kaskaede's Turn
Kaskaede drew a card.
Kaskaede's Ditto used Cavern Tackle on datamaru’s Radiant Greninja for 120 damage.

Turn # 7 - datamaru's Turn
datamaru drew Boss's Orders.
datamaru played Switch Cart.

• datamaru's Slither Wing was switched with datamaru's Radiant Greninja to become the Active Pokémon.
• datamaru's Radiant Greninja healed 30 damage.
  datamaru's Slither Wing is now in the Active Spot.
  datamaru played Iono.
• datamaru shuffled their hand.
• datamaru put 16 cards on the bottom of their deck.
  • Basic Lightning Energy, Briar, Boss's Orders, Pokégear 3.0, Night Stretcher, Fezandipiti ex, Energy Retrieval, Superior Energy Retrieval, Night Stretcher, Basic Grass Energy, Pokémon Catcher, Teal Mask Ogerpon ex, Earthen Vessel, Pokégear 3.0, Pokémon Catcher, Lost Vacuum
• Kaskaede shuffled their hand.
• datamaru put 11 cards on the bottom of their deck.
• datamaru drew Basic Lightning Energy.
• datamaru drew 4 cards.
  datamaru ended their turn.

Turn # 7 - Kaskaede's Turn
Kaskaede drew a card.
Kaskaede's Ditto used Cavern Tackle on datamaru’s Slither Wing for 120 damage.

Turn # 8 - datamaru's Turn
datamaru drew Briar.
datamaru ended their turn.

Turn # 8 - Kaskaede's Turn
Kaskaede drew a card.
Kaskaede's Ditto used Cavern Tackle on datamaru’s Slither Wing for 120 damage.
datamaru's Slither Wing was Knocked Out!
datamaru's Radiant Greninja is now in the Active Spot.
Kaskaede took a Prize card.
A card was added to Kaskaede's hand.

Turn # 9 - datamaru's Turn
datamaru drew Boss's Orders.
datamaru's Radiant Greninja used Concealed Cards.

• datamaru discarded Basic Lightning Energy.
• datamaru drew 2 cards.
  • Pokégear 3.0, Night Stretcher
  datamaru played Pokégear 3.0.
• datamaru shuffled their deck.
  datamaru played Night Stretcher.
• datamaru moved datamaru's Slither Wing to their hand.
  datamaru played Slither Wing to the Bench.
  datamaru ended their turn.

Turn # 9 - Kaskaede's Turn
Kaskaede drew a card.
Kaskaede's Ditto used Cavern Tackle on datamaru’s Radiant Greninja for 120 damage.
datamaru's Radiant Greninja was Knocked Out!
datamaru's Slither Wing is now in the Active Spot.
Kaskaede took a Prize card.
A card was added to Kaskaede's hand.

Turn # 10 - datamaru's Turn
datamaru drew Energy Retrieval.
datamaru played Energy Retrieval.

• datamaru moved datamaru's 2 cards to their hand.
  • Basic Grass Energy, Basic Fighting Energy
  datamaru's Teal Mask Ogerpon ex used Teal Dance.
• datamaru attached Basic Grass Energy to Teal Mask Ogerpon ex on the Bench.
• datamaru drew Pokémon Catcher.
  datamaru attached Basic Fighting Energy to Slither Wing in the Active Spot.
  datamaru's Slither Wing used Stomp Off.
• datamaru moved datamaru's Energy Retrieval to the discard pile.

Turn # 10 - Kaskaede's Turn
Kaskaede drew a card.
Kaskaede played Boss's Orders.

• datamaru's Raging Bolt ex was switched with datamaru's Slither Wing to become the Active Pokémon.
  datamaru's Raging Bolt ex is now in the Active Spot.
  Kaskaede's Ditto used Mad Bite on datamaru’s Raging Bolt ex for 460 damage.
  datamaru's Raging Bolt ex was Knocked Out!
• 2 cards were discarded from datamaru's Raging Bolt ex.
  • Basic Fighting Energy, Basic Lightning Energy
  Kaskaede took 2 Prize cards.
  A card was added to Kaskaede's hand.
  A card was added to Kaskaede's hand.
  Opponent took all of their Prize cards. Kaskaede wins.