From Bulbapedia, the community-driven Pokémon encyclopedia.
The King of Almia and the Three Princes is a folktale in Pokémon Ranger: Shadows of Almia.
Legend has it that long ago, even before it was filled with snow, Almia Castle was ruled by a king with three sons. The king wanted peace for Almia but his vigorous sons changed all this. He banished all three of his sons. One in red went to a volcano. One in yellow went to a desert. The youngest prince, one in blue, was allowed to stay. Over the years, the king felt guilty over his decision. Eventually, this caused darkness to consume him, forming the Shadow Crystal.
Tears of Princes
The Tears of Princes are a set of gems formed by the sons. They are written about in Brighton Hall's diary at the Altru Ruins in the Chroma Highlands. The diary is discovered by the player and Sven after finding the Shadow Crystal had been removed from the Chroma Ruins.
When all three gems are placed near the Shadow Crystal, they neutralize the darkness inside it, turning it into the Luminous Crystal instead. Due to this, the Sinis Trio attempt to secure at least one of the gems to prevent the power of the Shadow Crystal from being weakened.
Shards from the gems have the same effect but only at a lower level. These shards are apparently turned to pendants by some people, not knowing their true origin. Some examples would be several people who work at the Ranger Union that have these pendants. Linda and Rhythmi were given shards from the Red and Yellow Gems by Sven respectively. Murph obtained his blue one from his father who works at the Shiver Camp. These shards glow when they are near a shard from the Shadow Crystal. Like the gems, when three of the shards are together, they make the Dark Shard luminous. The shards from the Tears of Princes were placed in the player's Styler to make the Vatonage Styler.
The Blue Gem is a teardrop-shaped gem, and can be described as a bumpy Cascade Badge. It is found in Almia Castle and is guarded by a Lucario. Before the player can battle Lucario for the Blue Gem, they must battle Ice and his Froslass first. After he is defeated, two Riolu are required to destroy a barrier to reach Lucario. Sven flies around with it during Operation Brighton. It sounds somewhat like a trumpet.
The Red Gem is a fire-shaped gem that is found in the right entrance of Volcano Cave. It is guarded by a Heatran, but first, the player must defeat two Team Dim Sun Crimson Unit Admins and their Monferno. Then, Lavana will get involved and send an Infernape to fight. It must be captured to be able to battle Heatran, who will give the Red Gem when it is defeated. Wendy flies around with it during Operation Brighton. It sounds like a bell.
Cresselia and the Yellow Gem
The Yellow Gem is a crescent-moon-shaped gem found in the Hippowdon Temple. It is guarded by a Cresselia and after Cresselia is defeated, the gem is promptly taken away by Heath, who kidnapped Keith to use as a bargaining chip in exchange for the gem. After that, the Rangers and Team Dim Sun engage in a tug-of-war for the Yellow Gem at the Altru Tower. The player gets the gem out of the vault and gives it to Keith, but then Lavana knocks it away from him and leaves with it. However, when all three members of the Sinis Trio are defeated again, Ice will leave it behind. Keith flies around with the Yellow Gem during Operation Brighton. Its sound is an eerie high-pitched buzz.
The Shadow Crystal (Japanese: 闇の結晶 Dark Crystal) is formed by the king from the folklore; it was protected by Darkrai in the Chroma Ruins. Team Dim Sun planned to use this to power their Incredible Machine so they could take control of all the Pokémon. They stole the crystal from the ruins, even going through Spiritomb and Darkrai, and carried it to their Oil Field Hideout and then to Altru Tower.
Shards from this crystal, called Dark Shards are used by Team Dim Sun to enable their Gigaremo and Miniremo Units to hypnotize Pokémon. These are mined at the Chroma Ruins.
The Shadow Crystal was eventually transformed into the Luminous Crystal (Japanese: 光の結晶 Light Crystal) thanks to the power of the three gems. It was left at the top of Altru Tower, which became known as the Tower of Peace, along with the three gems. Its guardian still looked after it until Professor Hastings asked it to go, mentioning that the crystal will be safe there.
- Lucario is the only Gem Guardian that is not a legendary Pokémon, Cresselia is the only one not part Steel-type, and Heatran is the only one that is obtained in a fixed location in Diamond, Pearl, and Platinum.
- Cresselia is also the only one that is only one type.