On November 6, the Pokémon TCG welcomes Mega Evolution – Delta Reign, an expansion led by 
Mega Rayquaza-ex. For longtime collectors, though, the word “Delta” evokes something else entirely: a small Greek letter, δ, that appeared in 2005 on cards with completely unexpected types. A 
Charizard of the Darkness type, a 
Gyarados of the Fire type, a 
Mew of the Water type… Here is the story of δ Pokémon, one of the most original mechanics in the history of the card game.
2005: EX Delta Species and the Mysterious Holon Region
It all starts with the EX Delta Species expansion, released in late 2005 in the United States and in 2006 in France. It introduces a brand-new region, Holon, which exists only in the card game. The story told by the cards goes like this: researchers in Holon, on the trail of Mew, used electromagnetic waves that transformed the region’s Pokémon. Their types changed, sometimes spectacularly.
The scientists named these Pokémon with a Greek letter, δ (delta), making them the fourth category of Pokémon discovered in the game, after regular Pokémon, Pokémon-ex and ☆ Pokémon, known as “Star” Pokémon. On the cards, the mention “δ Delta Species” appears next to the name.
The Principle: An Unexpected Type, a Preserved Weakness
The golden rule of δ Pokémon is simple: their type changes, but their Weakness stays that of the original species. A 
Charmander δ thus becomes Lightning type while remaining weak to Water, like any Charmander. That makes for combinations that would otherwise be impossible, and it caught more than one opponent off guard.
- A frequent dual type: many evolved or legendary δ Pokémon receive a second type, almost always Metal
- Adapted attacks: attacks require Energy of the new type, for example Grass Energy for a
Trapinch δ of the Grass type - The same name: the δ mention is not part of the card’s name, so a deck cannot contain more than four cards with the same name, δ and regular versions combined
- Mixed evolutions: a δ version can evolve from a regular version, which makes it possible to build hybrid lines
Some cards even played with this identity. The 
Salamence δ from EX Delta Species attacks with Delta Blast, and an 
Ampharos δ had a Poké-Body that made all of its owner’s Pokémon cards count as δ Pokémon. Entire decks were built around these synergies.
Five Expansions and Nearly 170 Cards
The δ adventure lasted a little over a year, across five expansions of the EX era. Our card database lists nearly 170 of them, very unevenly distributed:
| Expansion | Release in France | δ cards listed | Key points |
|---|---|---|---|
| EX Delta Species | June 2006 | 32 | The first, with Mewtwo δ, Rayquaza δ et Metagross δ |
| EX Legend Maker | September 2006 | 1 | A single Pikachu δ, as a secret card |
| EX Holon Phantoms | May 2006 (United States) | 49 | The four Deoxys δ and Gyarados ☆ δ |
| EX Crystal Guardians | February 2007 | 11 | Charizard δ and Sceptile ex δ |
| EX Dragon Frontiers | May 2007 | 75 | Ten Pokémon-ex δ, Charizard ☆ δ and Mew ☆ δ |
EX Dragon Frontiers marks both the peak and the end of the mechanic. Almost the entire expansion is made up of δ Pokémon, including a series of very popular Pokémon-ex δ: 
Dragonite ex δ, 
Tyranitar ex δ, Rayquaza ex δ, Salamence ex δ, as well as 
Latias and 
Latios ex δ. After it, δ Pokémon disappear from new expansions.
The δ Cards That Became Legendary
If one category of δ cards left a mark on collectors, it is the ☆ δ Pokémon. These ultra-rare cards, with a golden finish and recognizable by the star next to the name, combined two rarities in one. A deck could contain only a single copy.
- Charizard ☆ δ (EX Dragon Frontiers): a Darkness-type Charizard, with the attack Dark Swirl dealing 150 damage
- Gyarados ☆ δ (EX Holon Phantoms): a Fire-type Gyarados, whose attack All-Out Blast gets stronger with discarded Energy
- Mew ☆ δ (EX Dragon Frontiers): a Water-type Mew able to copy the opponent’s attacks with Mimicry
These cards are among the most emblematic of the EX era, and their market value reflects that reputation. Before any purchase, it is best to compare recent prices and check the card’s condition carefully, as these rarities are also prime targets for counterfeiters.
From the Hoenn Delta to Delta Reign
The delta then found new life in the video games. In 2014, Pokémon Omega Ruby and Alpha Sapphire offered, after the main adventure, the “Delta Episode”, a story centered on Rayquaza and its Mega Evolution. Mega Rayquaza receives its exclusive Ability there, Delta Stream, which replaces the weather with violent air currents.
This is the legacy that Mega Evolution – Delta Reign calls upon. The expansion, which will hit stores on Friday, November 6, 2026, is led by Mega Rayquaza-ex, back in the TCG for the first time in more than ten years. It is joined by 
Mega Golurk-ex, 
Mega Malamar-ex et 
Mega Golisopod-ex, and the expansion introduces Legendary Stadiums, pairs of Stadium cards that form a panoramic illustration. To date, no δ card has been announced in the expansion: its name refers first and foremost to Mega Rayquaza and its Delta Stream.
Prerelease tournaments start on Saturday, October 24 in participating stores, and the expansion arrives in Pokémon TCG Live on November 5 (our full presentation).
Collecting δ Cards Today
Twenty years after their release, most δ cards remain affordable, with the exception of ☆ δ Pokémon and the most sought-after Pokémon-ex δ. A few tips to get started:
- Pick a common thread: a complete expansion, a Pokémon family, or all the δ Pokémon of a single type
- Check for the δ mention: it appears to the right of the name, and it is what sets the card apart from the regular version of the same Pokémon
- Watch the condition: cards from 2006-2007 have often seen heavy use, and whitened edges or scratches on holofoils weigh heavily on value
- Beware of counterfeits: for expensive cards, compare with reference scans and buy from reputable sellers (our guide to spotting them)
- Think about protection: sleeves and toploaders, or even grading for your centerpiece cards
Key takeaways
Between 2005 and 2007, δ Pokémon were one of the boldest ideas in the Pokémon TCG: new types, a region created for the occasion and ☆ cards that stayed in people’s memories. Delta Reign does not bring them back, but it puts the word back in the spotlight with Mega Rayquaza. The perfect excuse to dig out your binders. Do you have a δ card in your collection?
Sources: Poképédia, Bulbapedia, The Pokémon Company International (Delta Reign)
