Δ Delta Species are a special kind of Pokémon. It is often referred to as Δ, DS, or Delta.
Some time in the past, scientists and other people found the town of Holon in an attempt to locate the Mirage Pokémon Mew. Utilizing the unique magnetic properties of the area, the scientists built the Holon Research Tower in the center of the town to harness electromagnetic waves to track Mew's location. However, an unintended side affect of this caused the local Pokémon to mutate into abnormal Types inconsistent with their genes elsewhere. This new kind of Pokémon became known as Δ Delta Species.
Δ Delta Species Pokémon are mutated species whose Types are different than those defined in their genes. Pokémon that are normally monotype are given a second type, while dual-type Pokémon are given an entirely new Type combination. This can make for some unexpected battle results.
The Type of a Δ DS Pokémon tends to fluctuate quite a bit until it evolves into its final evolution. Trainers that use unevolved Δ DS Pokémon may find that their type fluctuates often.
Δ DS Pokémon still have the same weaknesses that a regular Pokémon of their species would have. For example, a Dark-type Pikachu would remain weak to Ground and Rock attacks, forcing Trainers to perform different strategies.
Appearance-wise, Δ DS Pokémon do not undergo any physical changes, but do gain an aura that denotes their changed Type. More powerful Pokémon have a more visible aura. This aura is only visible by those with an Aura Reader (most Shadow Hunters), or those with special capabilities (Riolu and Lucario).
- Δ Delta Species Pokémon are based off of the similarly named δ Delta Species Pokémon from the Pokémon Trading Card Game, used from EX Delta Species to EX Dragon Frontiers.
- The reasoning behind the capitalization of the Greek letter Delta is because lowercase Delta δ represents a change, while uppercase Delta Δ represents a major change, the latter of which being more accurate to Δ DS Pokémon's backstory.