Lake Guardians (anime)

The Lake Guardians or Lake Trio are a trio of Legendary Pokémon consisting of Uxie, Mesprit, and Azelf who are the protectors of the Sinnoh region in the Pokémon anime. Team Galactic wishes to take control of them and use their powers to create a new universe in the Pokémon world. Juniper, Saturn, and Mars were planning on bonding with them, but the trio bonded with Ash Ketchum, Dawn, and Brock instead. The Team Galactic leader, Cyrus, hired Hunter J to capture the lake trio so he would use them to create a new world.

Mesprit
Mesprit was the first of the lake guardians to appear in the anime. It chose to connect with Dawn because of her ability to sense the feelings of Pokémon. Dawn first encountered Mesprit at Lake Verity in Following a Maiden's Voyage!. After she had made friends with a stubborn Piplup, she crossed Lake Verity and saw the projected soul of Mesprit. It wouldn't be until The Needs of the Three! that Dawn would see Mesprit in its true form. Mesprit contacted Dawn in her dreams warning her of the destruction of the world. Mesprit was awakened from its sleep after Azelf was captured by Pokémon Hunter J. It and Uxie teleported to Lake Valor in order to try to save Azelf, but the two of them were also captured by J. Before being turned to stone, Mesprit and Uxie used Future Sight. When J was about to leave, the attack came from the clouds and struck her ship, sending it crashing into Lake Valor. Mesprit was able to contact Dawn through her thoughts. She was also able to feel its pain. Mesprit eventually teleported Dawn to the headquarters of Team Galactic. Cyrus was able to take control of Mesprit's mind with a piece of the Red Chain which he implanted in its forehead. He took it and the other lake guardians to the Spear Pillar where they were all used to awaken Dialga and Palkia. Dawn was able to successfully set Mesprit free by telling Piplup to use BubbleBeam to break the Red Chain piece that was controlling it. With their hearts bonded, Mesprit and Dawn were able to help calm down Dialga and Palkia and save the world from destruction. Afterwards, Mesprit said goodbye to Dawn and went back to sleep in Lake Verity.

Azelf
Azelf is the second lake guardian to appear in the anime. It chose to connect with Ash because he used his strong will power to protect Pokémon. Ash first encountered Azelf at Lake Valor in Pruning a Passel of Pals! after he was having a hard time sleeping because he was worried about how he would do in the Wallace Cup. In the middle of the night, he walked and looked out on Lake Valor where he saw Azelf's projected soul. It wouldn't be until The Needs of the Three! that Ash would see Azelf in its true form. Azelf contacted Ash in his dreams warning him of the destruction of the world. Azelf was awakened from its sleep after Pokémon Hunter J dropped the Galactic Bomb into Lake Valor. Ash actually felt the shock wave of the blast because of his connection to Azelf. Azelf tried to fight off J, but it was eventually captured. Mesprit and Uxie attempted to rescue it but they were captured as well. While at Galactic Headquarters, Azelf called on Ash and teleported him to the base. Cyrus was able to take control of Azelf's mind with a piece of the Red Chain which he implanted in its forehead. He took it and the other lake guardians to the Spear Pillar where they were all used to awaken Dialga and Palkia. Ash was able to successfully set Azelf free by telling Pikachu to use Thunderbolt to break the Red Chain piece that was controlling it. With their hearts bonded, Azelf and Ash were able to help calm down Dialga and Palkia and save the world from destruction. Afterwards, Azelf said goodbye to Ash and went back to sleep in Lake Valor.

Uxie
Uxie is the last of the lake guardians to appear in the anime. It chose to connect with Brock because of his vast knowledge of Pokémon. It is so far the only legendary Pokémon that Brock has befriended. Brock first encountered Uxie at Lake Acuity in Uncrushing Defeat!. Brock went in search for a berry near the lake that would help Ash's Monferno recover from its injuries that it received during its battle with Paul. When he looked out on the lake, he saw Uxie's projected soul. It wouldn't be until The Needs of the Three! that Brock would see Uxie in its true form. Uxie contacted Brock in his dreams warning him of the destruction of the world. Uxie was awakened from its sleep after Azelf was captured by Pokémon Hunter J. It and Mesprit teleported to Lake Valor in order to try to save Azelf, but the two of them were also captured by J. Before being turned to stone, Mesprit and Uxie used Future Sight. When J was about to leave, the attack came from the clouds and struck her ship, sending it crashing into Lake Valor. Uxie was able to contact Brock through his thoughts. He was also able to feel its pain. Uxie eventually teleported Brock to the headquarters of Team Galactic. Cyrus was able to take control of Uxie's mind with a piece of the Red Chain which he implanted in its forehead. He took it and the other lake guardians to the Spear Pillar where they were all used to awaken Dialga and Palkia. Brock was able to successfully set Uxie free by telling Croagunk to use Brick Break to shatter the Red Chain piece that was controlling it. With their hearts bonded, Uxie and Brock were able to help calm down Dialga and Palkia and save the world from destruction. Afterwards, Uxie said goodbye to Brock and went back to sleep in Lake Acuity.