This guide details how to obtain and utilize Hydreigon, a powerful Dark/Dragon-type Pokémon in Pokémon Scarlet and Violet. Hydreigon's pre-evolutions, Deino and Zweilous, are exclusive to Pokémon Scarlet, requiring trading or transferring to obtain them in Pokémon Violet.
Acquiring Deino and Zweilous:
Deino can be found in several locations within Pokémon Scarlet: Alfornada Cavern, Dalizapa Passage, Glaseado Mountain, Area Zero, and North Province (Area Two). Higher-level Deino (levels 35-40) reside in Alfornada Cavern and Dalizapa Passage, requiring Koraidon's high jump ability for access to the former. Three-star Tera Raids also offer a chance to encounter Deino, potentially with its Hidden Ability and a different Tera Type. Zweilous, Deino's evolution, appears in four-star Tera Raids and in the same wild locations as Deino.

To obtain Deino in Pokémon Violet, trading via the Union Circle (requires Nintendo Switch Online) or transferring from Pokémon HOME (compatible with Pokémon Sword/Shield, Pokémon GO, and Pokémon Scarlet) are necessary. Transferring via HOME involves moving Deino from your HOME Basic Box to your Pokémon Violet PC Box.
Evolving Deino:

Deino evolves into Zweilous at level 50, and Zweilous evolves into Hydreigon at level 64. Exp. Candy L and XL are recommended for faster leveling. Auto-battling can also expedite this process.
Hydreigon's Strengths and Weaknesses:

Hydreigon boasts a base stat total of 600, excelling in Special Attack and Attack with good Speed. A Timid or Jolly Nature enhances its Speed.
| Stat | Base Stat |
|---|---|
| HP | 92 |
| Attack | 105 |
| Special Attack | 125 |
| Defense | 90 |
| Special Defense | 90 |
| Speed | 98 |
| Total | 600 |
Type Effectiveness:
Terastallizing mitigates Hydreigon's 4x weakness to Fairy-type moves. Its movepool allows for both physical and special attacking strategies. Flash Cannon (via TM) is a crucial Steel-type move to counter its Fairy weakness. Other recommended moves include Nasty Plot, Dragon Pulse (or Draco Meteor), and Dark Pulse.
This revised guide provides a comprehensive overview of acquiring, evolving, and effectively utilizing Hydreigon in Pokémon Scarlet and Violet.