The Pokémon TCG: EX Emerald expansion was released on May 9th, 2005.

EX Emerald

The new EX Emerald expansion is a bit different from other expansions. Many of the cards in EX Emerald work really well with cards from other expansions. Some of the cards in EX Emerald are re-released Trainer cards, so you can strengthen many of your current and new decks, and there are three new Trainer cards that can further improve your decks. Useful Special Energy cards, as well as collectible holographic basic Energy cards, are in EX Emerald as well. There are quite a few Stage 1 Pokémon-ex that are likely to be useful in a variety of situations. Since the new Pokémon Emerald video game has a new forme of Deoxys, a new Deoxys and a new Deoxys ex are available. Finally, there are new legendary Pokémon-ex that team up with the earlier Pokémon-ex from EX Hidden Legends.

Cooperation is the Key
EX Emerald's Pokémon are very familiar to veteran Pokémon TCG players. That's because many Pokémon with the same names were released in expansions such as EX Ruby & Sapphire and EX Hidden Legends. What does that mean for the typical player? One important rule in the Pokémon TCG is that you may only have a maximum of four cards with the same name (excluding basic Energy cards). Now that new variants of Pokémon have been released in EX Emerald, you can create decks with more flexible strategies.

Two Sceptile were originally introduced in EX Ruby & Sapphire, and one of them (EX Ruby & Sapphire, 20/109) allowed you to move Grass Energy between your Pokémon. The new Sceptile (10/106) prevents Special Conditions on your Active Pokémon if they have Grass Energy attached. If you use the two Sceptile together, you can prevent Special Conditions from ever bothering you!

Two Swampert were also introduced in EX Ruby & Sapphire. One of those Swampert (EX Ruby & Sapphire, 23/109) lets you attach an extra Water Energy from your hand onto your Active Pokémon, so you can add two Energy per turn if you have enough Energy in your hand. The new Swampert (11/106) lets you move Water Energy from your Active Pokémon to your Benched Pokémon. That means that you can quickly distribute your Water Energy as necessary while placing twice as much Energy as usual! You might even have a Swampert ex (EX Team Magma & Aqua, 95/95) waiting on the Bench, gradually gaining enough Energy to do 100 damage per attack. Or you might use Island Cave (EX Hidden Legends, 89/101) with the new Swampert: you could place Water Energy on a Fighting-type, Metal-type, or Water-type Pokémon to remove all Special Conditions from it, then use the new Swampert's Poké-Power to move that Water Energy somewhere else.

Gardevoir (EX Ruby & Sapphire, 7/109) lets you search your deck for a Psychic Energy card and attach it to a Pokémon, but you also have to put two damage counters on that Pokémon. The new Gardevoir (4/106) can remove two damage counters from a Pokémon, though. When you use both Gardevoir together, you can attach the extra Energy to your Pokémon and then remove the two damage counters! So, as with the Swampert combo, you can attach Energy twice per turn. That helps out Pokémon like Gardevoir ex (EX Sandstorm, 96/100), whose damage is based upon the amount of Energy in play. The new Gardevoir's healing ability also makes Gardevoir ex's 150 HP last a lot longer!

Say Hello to Old Friends and New
The question is, of course, how you could possibly put two or more Stage 2 Pokémon into play rapidly? EX Emerald helps you solve this problem with the re-release of several highly desirable Trainer cards, as well as new Trainer cards never seen before!

To evolve your Pokémon quickly, EX Emerald brings back Wally's Training (85/106) and Rare Candy (83/106). Wally's Training allows you to search your deck for an Evolution card that one of your Active Pokémon can evolve to. If you find one, you may place that Evolution card on that Active Pokémon. That means that you don't have to rely on luck to draw an Evolution card from your deck. You can even use it after you have already evolved that particular Pokémon that turn, so you can potentially get a Stage 2 Pokémon into play on your second turn. Rare Candy lets you evolve a Pokémon to its Stage 1 or Stage 2 form. Since Rare Candy is not a Supporter card, you may even be able to evolve a Basic Pokémon to its Stage 2 form on the first turn of the game!

In order to get an Evolved Pokémon into play, you'll need its Basic Pokémon in play first. Lanette's Net Search (77/106) has been re-released, and it lets you search your deck for up to three different types of Basic Pokémon. You'll be able to get all sorts of Pokémon into your hand and ready for evolution! It works well with Wally's Training because you can get the Basic Pokémon into your hand with Lanette's Net Search, play them onto your Bench, then evolve one on your next turn with Wally's Training.

New Basic Pokémon-ex
The Pokémon Emerald video game introduces a new Speed Forme for Deoxys, so the EX Emerald expansion does the same with Deoxys (2/106) and Deoxys ex (93/106)! Like the earlier Deoxys and Deoxys ex, the new Deoxys and Deoxys ex have the Form Change Poké-Power, so you can switch forms at will. Deoxys' Swift can do 30 damage for two Energy, and it ignores all effects on the Defending Pokémon. Deoxys ex's Fastwave does 50 damage for three Energy, and it ignores all effects on the Defending Pokémon except for Weakness. That means Deoxys ex can Knock Out a Wobbuffet (EX Sandstorm, 26/100) with one hit, even though Wobbuffet is normally immune to attacks from Pokémon-ex.

Regice ex (98/106), Regirock ex (99/106), and Registeel ex (100/106) return to the Pokémon TCG in an interesting new way. These new versions of the Regi-Pokémon react to the presence of other Regi-Pokémon (yours or your opponent's). You can create some interesting strategies by playing one or more of them together. For example, you can pair Regice ex with Regirock ex to help Regice ex remove Energy cards from your opponent. You can use Registeel ex with Regirock ex to give Regirock ex a damage boost. Registeel ex can Confuse opponents if Regice ex is in play. You can also mix in the EX Hidden Legends versions of them for even more flexibility in your strategy.

Don't forget that Lanette's Net Search lets you search your deck for any three different types of Pokémon, so you could get your Deoxys, Deo xys ex, Regice ex, Regirock ex, or Registeel ex into your hand very easily with it!

Source: https://www.pokemon.com/us/pokemon-tcg/ex-emerald