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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 the gems have the same effect but only at a lower level. These shards are apparently turned to pendants by some people, unknown of 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 Blue gem is a teardrop shaped gem that also looks like a Cascade Badge but bumpier. It is found in Almia Castle and is gaurded by a Lucario. Before you can battle Lucario for the Blue Gem you must battle Ice and his Froslass first. After he's defeated you still need two Riolu to open a barrier of some sort to be able to battle Lucario. Sven flies around with it during Operation Brighton.
The Red Gem is a sun shaped Gem that is found in Volcano Cave (the right entrance). It is guarded by a Heatran but first you have to defeat two Team Dim Sun Crimson Unit Admins and their Monfernos. Then Lavana will get involved and send an Infernape at you. Defeat it and you can go battle Heatran who will give you the red gem when you defeat it. Wendy flies around with it during Operation Brighton.
The Yellow Gem is a crescent moon shaped gem found in the Hippowdon Temple. It is gaurded by a Cresselia and after you defeat it you have to trade it for Keith with Heath, who will then send a Magnezone for you to face. After that the Rangers and Team Dim Sun engage in a Tug-of-War for it at the Altru Tower. The player gets it out of the vault and gives it to Keath but then Lavanna knocks it off him and leaves with it but after you defeat all three of the Sinis Trio again then Lavanna just leaves it behind. Keith flies around with it during Operation Brighton.
The Shadow Crystal is formed by the king from the folklore. It is 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 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 looks after it but was asked to go, mentioning that the crystal will be safe there.