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 a starter Pokémon on behalf of Professor Sycamore. He is then met at the Pokémon Center in Santalune 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.
"All right! Nice to meetcha! You know, it'd feel like we were a closer crew if we called each other by nicknames. Can I call you <player's name's first letter>-Meister/Lady <player's name's first letter>?"
"I know right? It was such a cool feeling when Trevs and I met our Pokémon! Hope you feel the same way we did!"
"Oh lighten up, Trevs! You're way too serious sometimes. Um, <player's nickname>... Please take this with you, too. It's a letter from the professor. He said you should give it to your mom."
"All right! We're done with our errand for the professor. I guess Trevs and I will go look for Pokémon! Let's go, Trevs!"
"Oh! Hey there, <player's nickname>! Are you here to get your Pokémon healed, too? Pokémon Centers sure are great. You can talk to the lady at the counter and have her heal your Pokémon. And you can even deposit Pokémon you've caught in that PC! Know how Pokémon are sent to a PC when you've caught more than you can carry? That's where they go! Oh yeah, <player's nickname>! There's a Poké Mart in the back of a Pokémon Center. IT's a good idea to stock up on Poké Balls and Potions and stuff at the Poké Mart, too."
"No clue, but it seems hush-hush. I AM curious about what's going on, but we should probably stay out of it."
"Hey, <player's nickname>! To get to Camphrier Town, leave the lab, turn left, and go straight. That Café Soleil Calem/Serena was talking about is over that way, too.
"Yeah! They're just like a dance team made up of Pokémon, aren't they?"
"Nope! Even during Pokémon battles, I'm always checkin' out their moves! And then my feet just starting moving, too! I can't even help it, y'know? Like with Swords Dance! I love it! I guess that's why I can never win…"
Before battle
"Oh, hey, it's <player's nickname>! Do your Pokémon know any sweet moves? Show me in a battle!"
When defeated
"That was some nice footwork!"
After being defeated
"Well, yeah, Trevs! Coming up with the world's best Pokémon dance IS my dream, after all! I was born to dance! I won't ever stop! Not with moves like this!"
"Man, I really want to meet a Pokémon that can use the move Teeter Dance. Then I'd wanna dance with it, right?"
"Oh, hey, <player's nickname! Trevs said he wants to check out the Pokémon Day Care. Come with us!"
Inside Daycare
"Wow! A Pokémon will come out? Maybe I'll leave some Pokémon here! Having the same Pokémon with the same moves might step my dance up! How about you, <player's nickname>?"
"Well, I'm gonna go look for some Pokémon for my dance team!"
In the flowers
"Hey, <player's nickname>, have you seen Dunsparce?
After being defeated in tag battle
"Whoa... Now THAT was a nice move!"
After battle
"Win or lose--either way, you gotta smile! If your Pokémon see you getting down in the dumps, they might be less confident."
"Hey, <player's nickname>! How's your journey going?"
"Get this! I've found some great Pokémon dancers!"
"That's right! He did say that! Ummm... Who were we supposed to say hello to again?"
"Oh, that's right! He did say that! Well, I guess we should look for the Mega Evolution guru, then! Where do you think he is anyway?"
On beach section
"<player's nickname>, check this out! Isn't this stone cool? I got it from this person called the wandering stone collector for showing off my dance moves! It might be a Mega Stone! Here, <player's nickname>, you can have it!"
Thanks!:
Are you sure?:"I want you to have it, 'cause you're such a great Trainer and all... I still remember our battle on Route 5."
"That's the Tower of Mastery? Sooo cool! Well, I'll go call Trevs, then. Go on ahead, OK?"
"Yep! As you can see, we're doing great! Thanks for asking! We worked together to save the Pokémon connected to the stones on Route 10! I mostly left battling with Team Flare to Sina and Dexio, though..."
"<Player>! Can we have a Pokémon battle? Oh, uh...sorry to just throw that at you..."
When defeated
"It's weird, but… I don't get that down when I lose to you."
After being defeated
"Geosenge Town made me think… If <player> hadn't been there, I wouldn't be dancing now, that's for sure. That made me want to get to know <player> better, and I thought a battle would be the best way to do that. It's kinda selfish of me, I guess. But it's also a way of thanking him/her!"
"He's/She's off training with the Mega Evolution guru. He/She said friends are friends even if they can't be together."
In Pokémon Adventures, Tierno is an aspiring dancer. Additionally, he is childhood friends with X, Y, Trevor, and Shauna. He is first seen standing in front of X's house while watching one of Y's failed attempts to get X to leave his house. He questions why Shauna even bothers coming with them when she believes that their attempts will end in failure. She replies that she holds onto the hope that they can one day come together as friends again. Their attempts are cut short when the legendary Pokémon Xerneas and Yveltal have appeared and have started fighting, causing Vaniville Town to be destroyed in the chaos.
Although Y manages to get everyone to safety with her Rhyhorn, Tierno is horrified to see his favorite dancing school get destroyed in an explosion. After the chaos had ended and the five friends grouped together, Tierno wonders what they will do now that their home is gone. To find some answers, the group sets off on an adventure as friends again.
Corphish is Tierno's only known Pokémon. It was first seen with its Trainer in Vaniville Town in front of X's house. Later, it escaped from the rampaging Xerneas and Yveltal.
Tierno was introduced as a Supporter Card in the Pokémon Trading Card Game at the beginning of the English XY Series (the Japanese XY Era). First released in the Japanese XY Beginning Set, the Tierno card later debuted in the English Kalos Starter Set, with both prints featuring an illustration based on the Ken Sugimori artwork of the character. With the same effect as Cheren from the Emerging Powers expansion, Tierno allows the player to draw three cards from their deck.
