Bittercold

The Bittercold is the main antagonist and the final boss of Pokemon Mystery Dungeon: Gates To Infinity. A large crystalline creature that resides in the Glacier Palace, it is made from negativity from other Pokemon, and it manipulates other Pokemon into stopping humans who entered the Pokemon world.

Story
When the player and other Pokemon explore the Glacier Palace for the first time, they discover floating ice crystals, at this point it was 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 told the player that they must destroy the Bittercold. Later in the story, it was revealed that Kyurem guards the Bittercold to protect it's future, which would lead to the end of the world. When the player and other Pokemon reach to the Glacier Palace.

When the player and their partner reached to the Bittercold, the characters felt 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 asked the player to use remaining strength at it, and the player charged and damaged it, revealing a red core, it's weak point. After this, a rainbow temporarily appears in sight of Pokemon 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 was battled again, when this time it is vulnerable. After the battle, the player finally destroyed the Bittercold, resulting the wind of despair to disappear again and soon the Glacier Palace broke and fall from the sky.

Trivia
It's Japanese name means Glacial Body.

It has many similarities to Dark Rust of Pokemon Rumble Blast. They are non-Pokemon villains who are final bosses in the game their at, possess dark powers, and were invincible in the first battle.