The Bittercold is the main antagonist and the final boss of Pokémon Mystery Dungeon: Gates To Infinity. A large crystalline creature that resides in a void in the Glacier Palace, it is made from negativity from Pokémon, and it manipulates them into stopping humans who entered the Pokémon world.
When the player and other Pokémon explore the Glacier Palace for the first time, they discover floating ice crystals, at this point it is a mystery. The Bittercold was first mentioned by Hydreigon after escaping from Munna's gang while conversing the player the gang's motives, this moment explain the reason why floating ice crystals appear when the player recall their memories in the Glacier Palace. Hydreigon tells the player that they must destroy the Bittercold. Later in the story, it was revealed that Kyurem guards the Bittercold to protect its future, which would lead to the end of the world.
When the player and their partner reached to the Bittercold, they feel pain as they approach to it by the wind of despair, though the player is the only one capable of fighting it without complete suffering since it is actually a human. The characters who support the player urge the player to encourage their hope to defeat the Bittercold, initiating a battle against it. The Bittercold use attacks that can cause stat drops or confusion to the player and was invincible.
After the first attempt, the player realized that it does not seem to be damaged and became unsteady. Soon after this moment, the partner asks the player to use remaining strength at it, and the player charges to it, damaging it and revealing a red core, its weak point. After this, a rainbow appears in sight of Pokémon Paradise, but it disappears and the winds of despair reverts back. The characters urge the player again to defeat the Bittercold with the voices of encouragement, helping the player once more. It is battled again, this time vulnerable. After succeeding the battle, the player destroys the Bittercold, resulting the wind of despair to disappear again and soon the Glacier Palace broke and fall from the sky. Its influence on other Pokémon also fades.