The Pokémon TCG: EX Team Magma vs Team Aqua expansion was released on March 15th, 2004.

EX Team Magma vs Team Aqua

EX Team Magma vs Team Aqua introduces 95 new cards to the Pokémon-e Trading Card Game. Many of these cards are associated with either Team Magma or Team Aqua, who are two groups committed to conquering the world through the control of the land or the sea. Both teams have trained some of their Pokémon to have dual types, making them extremely dangerous! They have also trained some of their Pokémon to specialize in attacks that match their team's philosophies. However, this kind of rigorous training takes a lot of time and effort, so normal Pokémon can't evolve into (or from) Team Magma or Team Aqua Pokémon. With these new twists to the rules come new strategies!

Dual Types
Both Team Magma and Team Aqua have begun training Dual Energy type Pokémon. Dual-type Pokémon have two types simultaneously, so they are more likely to exploit another Pokémon's Weakness! In this card expansion, all dual-type Pokémon have the Darkness type as one of their types, so they can use Darkness Energy to increase the damage of their attacks. However, with the exception of Team Aqua's Walrein and Team Magma's Aggron, dual-type Pokémon have only one Weakness. And, except for Team Aqua's Manectric (4/95), no dual-type Pokémon has a Resistance.

Damage Control
Some of Team Magma's Pokémon have attacks that allow you cause damage to any Active or Benched Pokémon. For example, Team Magma's Claydol (33/95)'s Clay Curse lets you place 2 damage counters on your opponent's Pokémon in any way you like. Team Magma's Aron (59/95)'s Dig Under does 10 damage to any of your opponent's Pokémon, regardless of Resistance. You can injure the most dangerous Pokémon that your opponent has in play in order to exploit another advantage of Team Magma's Pokémon: many of them have attacks that cause extra damage or Special Conditions to previously injured Pokémon!

Combine the two attack methods for maximum impact! For example, with the Land Sonic attack, Team Magma's Lairon (36/95) will hit for 40 damage. It will also Confuse a Defending Pokémon with damage counters on it! Or consider Team Magma's Houndoom (34/95)'s Damage Burn: if the Defending Pokémon already has any damage counters on it, the attack does 40 damage plus 20 more damage!

Also consider using older Pokémon that have bench-hitting abilities, such as Xatu (EX Sandstorm, 55/100) with Team Magma Pokémon. Xatu puts a damage counter on each of your opponent's Pokémon, guaranteeing that your Team Magma Pokémon can use their damage-amplifying attacks on the next turn. Xatu also has no Retreat Cost, so you can make a Benched Team Magma Pokémon become Active for free!

The Team Magma Hideout Stadium card will work wonders for Team Magma's Pokémon, too. If your opponent plays a Basic Pokémon that doesn't have Team Magma in its name from his or her hand, that player puts one damage counter on that Pokémon. This means that your Team Magma Pokémon can gain the extra effects of their attacks right away!

Energy Fluctuations
Are you having problems getting Energy at the right time? With EX Team Magma vs Team Aqua, there are now even more ways to get the Energy you need!

If you need to find basic Energy cards in your deck, the new Team Magma Conspirator (82/95) and Team Aqua Conspirator Trainer (77/95) cards allow you to search your deck for up to two Basic Energy cards of your choice. You could even use the Conspirators in decks that contain no Team Magma or Team Aqua Pokémon!

Source: https://www.pokemon.com/us/pokemon-tcg/ex-team-magma-vs-team-aqua