Tierno is a hero from Pokémon X and Pokémon Y and the main Pokémon anime.
In the games
Tierno appears in Pokémon X and Y as a friend of the player, to whom he gives the starter Pokémon sent through him by Professor Sycamore. He is a dancer and his goal is to create a dance team with Pokémon and wants to find Pokémon with amazing moves. As such, the Pokémon in his party know "dance" moves such as Swords Dance and Petal Dance.
Tierno is first met in Aquacorde Town, where he delivers the player and two of his or her friends astarter Pokémon on behalf of Professor Sycamore. He is then met at the Pokémon Center inSantalune City, where he gives the player a minor tutorial on what is in the Pokémon Center.
Tierno is first battled on Route 5, and then again on Route 7, albeit this time with Trevor. Tierno is next met in Reflection Cave, where he gives the player a TM containing Flash.
After the completion of the story line, Tierno can be found in Coumarine City, asking to see a Pokémon which contains a randomly selected dancing move each day.
Tierno also appears as one of the player's partners in the Battle Maison when choosing Multi Battle.
In the anime
Tierno debuted in Summer of Discovery! along with Shauna and Trevor, and his Squirtle. He first had a battle against a trainer's Conkeldurr and won. Later that episode, he battled Ash's Froakie. During his battle with Ash, he revealed that he dreams of forming a dance unit with his Pokémon. He also was seen in a flashback in Showdown at the Shalour Gym!.