Summary
The 2005Pokemon TCGset Delta Species introduced the eponymous “Delta Species” card type, which featured type-shifted Pokemon for the first time in the game’s history. These unique ‘mons were a big hit, and, as such featured heavily in other sets that followed it: Holon Phantoms, Crystal Guardians and Dragon Frontiers.
While these cards might not reach the monetary heights of cards from, say, 2003’s Skyridge or the iconic cards from 1999’s Base Set, they’re still eminently intriguing due to changes in typing as well as the fact that the Delta Species cards are also dual types – a trait that debuted in 2004’s Team Magma vs. Team Aqua set.

The card prices quoted all come fromPriceCharting’s median sales value over the past calendar year and may fluctuate over time. Many of the cards included herein do not have median values on TCGPlayer.com due to their immense scarcity.
10Vaporeon – Holofoil Rare
Market Price: $48.61
While the Eeveelution cards featured in Delta Species don’t reach the heights of themost valuable Eeveelution cards of all time, they certainly qualify among the most valuable cards from their own set.
Eeveelutions are always eminently popular, and Eevee’s water-type evolution kicks things off – this time as a dual-type water/metal Pokemon card. This Vaporeon’s second attack dealt an impressive (for the time) 50 damage for three energy, and if your foe’s ‘mon was behind on energy, this attack could hold them at bay indefinitely.

9Espeon – Holofoil Rare
Market Price: $49.00
Following up Eevee’s water-type evolution is its psychic type, Espeon. Of course, in its “Delta Species” form, this Espeon is both a psychic type and a metal type – an interesting combination which surely impacts this card’s near-$50 price point.
This card also features some intriguing Ryo Ueda artwork that shows an unusual semi-bird’s eye angle of Espeon traipsing across what seems to be a bridge over sickly green water. Unusual and eye-catching.

8Umbreon – Holofoil Rare
Market Price: $50.00
While this card wasn’t mentioned onPokemon TCG cards that tell a story, this Umbreon card features striking artwork from Ryo Ueda that seems to show Eevee’s dark-type evolution sauntering down the same bridge that Espeon is on.
What are they planning on doing? Battling it out? Plotting to overthrow their trainers? Either way, this standard holofoil Umbreon will cost you a 50-piece on the secondary market.

7Mewtwo – Holofoil Rare
Market Price: $50.81
Mewtwo is always a popular subject when it comes to Pokemon TCG cards, but you’ve never seen one like this before. A dual fire/metal-type ‘mon, this Mewtwo features striking art (again by set all-star Ryo Ueda) that shows an energy-charged, fuchsia-colored Mewtwo ready to clobber an unsuspecting Pokemon or trainer.
This card’s ability and attack also synergize well, though the ratio of only damaging your foe 10 times the amount of energy attached was fairly weak at the time and more or less laughable by today’s standards.

6Dragonite – Holofoil Rare
Market Price: $53.59
Yet another card with tremendous artwork by 3D specialist Ryo Ueda in Delta Species, Dratini’s final evolution is shown here in full flight and lightly shimmering – perhaps representing this Dragonite’s dual lightning and metal typing.
In terms of gameplay, Dragonite features the ever-popular (and powerful) Agility attack, which, upon winning a coin flip, gives the ‘mon immunity from all damage and effects from an opposing ‘mon’s attack next turn.

5Flareon – Holofoil Rare
Market Price: $61.09
Yet another Eeveelution graces this list, and this time it’s Flareon, although in this case Flareon’s “Delta Species” makes it a dual fire/metal-type. It’s not every day that Mewtwo and Flareon share the same type of combination!
Featuring striking, action-packed art by Kouki Saitou, this card will set you back $20 more than its Flareon ex counterpart, which technically features a higher rarity (Ultra Rare) than this card. Perhaps it’s the flat holofoil method that gives this card its price point over $60.

4Umbreon – Reverse Holofoil Rare
Market Price: $85.83
Another reverse holofoil with a price point approaching triple digits, this Umbreon is almost identical to the standard holofoil one that goes for $50 on the secondary market in terms of design – though the Pokemon’s name and HP are both gold instead of black.
While over $85 is nothing to sneeze at, this card’s value pales in comparison to the top three cards on this list.

3Groudon Star – Holofoil Rare
Market Price: $294.65
The box art ‘mon from Pokemon Ruby (and Omega Ruby) receives its first-ever shiny variant within the TCG in Delta Species, and the popularity of shiny forms – especially on legendary ‘mons – means this card’s price point is stratospheric compared to the previous seven cards on this list.
With striking frame-breaking artwork and an eye-catching full-card Cosmos holofoil style, it’s no surprise that this card is worth nearly $300 close to 20 years after its release.

2Metagross Star – Holofoil Rare
Market Price: $335.00
Another shiny variant via its “Star” treatment, this pseudo legendary (aka “Powerhouse Pokemon,” which ispotentially the official name for such ‘mons) metal-type Pokemon showcases the amazing shiny form of Metagross, which replaces its teal and silver colors with a glittering silver-and-gold color scheme.
Again, these Star cards feature awesome artwork, a striking foiling method, and (for the time) impressively strong attacks – notably, like past Shining cards, this card is a basic Pokemon and does not have to be evolved to be played.

1Kyogre Star – Holofoil Rare
Market Price: $433.04
By far the most valuable card from Delta Species is Kyogre Star, which features a shiny version of the box-art ‘mon from Pokemon Sapphire (and Alpha Sapphire). This card clocks in at nearly $100 more valuable than the second-most valuable, so you know this is a top-tier chase card.
Featuring sterling artwork of a shiny Kyogre breaching the ocean by Masakazu Fukuda, this card showcases the truly superlative design of Star TCG cards. Beautiful full-card foiling combines with synergistic attacks and awesome artwork to make this a true masterpiece of a Pokemon TCG card, and it’s certainly deserving of its over $400 price tag.