Lake Guardians

The Lake Guardians, also known as the Lake Trio, refer to describe the Legendary Trio that reside on the three lakes of Sinnoh: Uxie, Mesprit and Azelf. They are the beings and symbolize the traits of knowledge, emotion and willpower respectively. All three of them share the same type, being Psychic-type, and share the same ability: Levitate, which makes them immune to Ground-type moves. They have appeared in the series In a Locked Room but made first appearances separately.

History
Based on the beliefs from sources, it is said that the Lake Guardians were born from the same egg. They were originally of one being, but due to a mysterious accident,  it was split into three. As soon as that happened, the traits they represent were spread to the other creatures that were born. The traits knowledge, emotion and wisdom form a perfect heart of a creature when fully fused. However, no one can form this perfection.

Years have passed, and the Lake Guardians are only seen as mirages. Uxie resembles a small yellow pixie wandering around the libraries around, finding, gaining and spreading knowledge to those who are near it. It also is believed that it looks after the cosmos sometimes and gains more knowledge about the universe as a whole. Mesprit resembles a pink water sprite that swims on the water, although it is mostly on its lake, being Lake Verity. It also makes water creatures and anyone who it has passed be happy and confident, and dares to help anyone with a single action. Azelf resembles a blue strong elf that resides on abandoned structures. It is believed that it used to be happy, but became serious after being threatened a lot, but this is how it spreads willpower, too. All of them are rumors, however, and is unknown if those actions are true.

The Lake Guardians refuse to reveal their true forms to anyone that are not capable of their traits. If any things come to worst, they will dare to pick their Chosen Ones, and that action will be permanent until a Chosen One dies. They will help them improve themselves and possibly gain a new form. This is a belief that came true, as people tried to find them and keep at least one of them to prove themselves worthy. However, most of them weren't worthy enough for them. In the end, during the Locked Room Challenge, Uxie's Chosen One is Rosalina because of her vast an great knowledge about the universe, Mesprit's is Yoshi because he expresses emotions when he needs to at the Yoshi Clan, his allies and friends, and Azelf's is Klitz because he has gone through tough experiences and wants to become stronger and stronger after his (almost) complete personality change.

They have never appeared as a whole group at the moment in the series In a Locked Room. Uxie first appears in Mass Attack, Mesprit first appears in Popping Party at the Monkey City, and Azelf first appears in Skyline Pigeon. Both Uxie and Mesprit reappear in Pirates of Solitaire, and Azelf has yet to make its second appearance.

Uxie

 * Main Article: Uxie

Uxie acts as the leader of the Lake Guardians, and is the being of knowledge. It is calm, mature, composed and someone who plans ahead. It is also caring, not wanting to harm the other two members, Mesprit and Azelf, and usually tells them what to do. It truly watches its surroundings, sometimes the cosmos, and tends to stay in libraries before choosing its Chosen One. However, it gets very orderly and doesn't want to be too late at important situations to be solved. It almost never gets outsmarted, but does not want to lose just because of luck. It also hates getting distracted. Uxie resides at Lake Acuity.

Mesprit

 * Main Article: Mesprit

Mesprit gets to be the expressive member of the Lake Guardians, and is, in fact, the being of emotion. It is defined as very sweet and likes anything cute, especially exotic creatures, but this brings the Lake Guardians into trouble when it comes for them not to be revealed in public. It is also sensitive, and tends to dislike getting touched by others other than its Chosen One. It thinks anything can be solved if anyone can control emotions well. It also thinks that doing so will lead to a strong potential to those close to her. It can get talkative and hates being lonely unless it's on a mission. Mesprit resides at Lake Verity.

Azelf

 * Main Article: Azelf

Azelf is a strong-willed member of the Lake Guardians and the being of willpower. In battle, it likes to get aggresive, and pretends to be tough. It may be quick to commence a battle, but it results to it constantly being reckless. It likes to defend its choices and tends to end up getting in an argument with Mesprit. It likes to get things done quickly, making it impatient, and is usually the first is most of the actions out of the three. It is even the first who chose its Chosen One, although with a short gap. It hates being referred as male or any of the members with a gender, because it thinks people should know they are all genderless. Azelf resides at Lake Valor.

Battle Style Comparison
Uxie is defensive, having its stats more on the defense side. It also gets strategic, and uses most of the time to think and act. It endures most attacks, then it will proceed to lower its enemy's capabilities. When enough time is stalled or at certain situations, it will erase a target's memories, as it is its natural ability.

Mesprit is the balanced member, and doesn't think of strategies or moves to use a lot. It likes to taunt its enemies by protecting itself and its allies from damage of lucky (critical) hits. It will tend to copy its enemy's movements. However, when the moment is up, it will sacrifice itself to heal its allies.

Azelf is offensive, having its stats more on the offense side. It will keep attacking no matter what the cost, being the aggresive member. However, because of this, it tends to be the first to get knocked out. It won't use the time to think at all. It can also summons from the ground if the place is clear enough.

Trivia

 * Originally, the Lake Guardians would not have actual personalities to display like in the official Pokemon sources, but this was changed in an attempt to make them reflect with their Chosen Ones.
 * They were known as the Unidentified Mysterious Animals before their names were revealed. Coincidentally, they match the initials of the Lake Guardians.
 * All members can learn sarcificing moves (Uxie for Momento, Mesprit for Healing Wish, and Azelf for Explosion).