Staff of the Frost Hydra

The  is an extremely powerful staff. When used, it spawns a light blue dragon that spits out frost at nearby enemies (and enemy players). The Staff of the frost Hydra is extremely powerful, as the monster spawned deals 102 damage and can target enemies on its own. This staff is useful when dealing with large groups of enemies such as the Goblin Army or Pirate Army.

To obtain the staff, one can kill any monster inside the Snow Biome while the world is in Hard Mode; these mobs have a low chance (1/4000) to drop a Frozen Key Mold, which is a material to craft the Frozen Key. This key will unlock a Frozen Chest in the Dungeon, which are randomly spawned (so some dungeons may not contain one). The chest will contain the staff (100% chance) as well as other items such as bars, potions, etc. It can also be found in gold chests (albeit extremely rarely).

Trivia

 * The creature spawned is not a hydra, but is in fact a Wyvern.