Let’s discuss Pokémon Evolution
I’ll get into the details within each entry, but as of the release of Extradimensional Crisis (A3a), we have three different Stages of evolution in Pocket: Basic, Stage 1, and Stage 2. I also will touch upon Fossils, as well as any cards that affect evolution in general.
Basics
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Basic Pokémon require no other cards to be put into play, nor do you have to wait to put them into play. This gives Basic Pokémon a one card and one turn advantage over Stage 1 Pokémon, a two card and two turn advantage over Stage 2 Pokémon, or a two card and one turn advantage over a Stage 2 evolved via Rare Candy (A3 144). The sooner you can get a Pokémon into play, the sooner you can benefit from it. The fewer deck slots a Pokémon requires can leave room for other Pokémon and/or Trainer cards.
There are five pieces of Basic Pokémon support: Celestic Town Elder (A2a 073, 088), Combee (A2 017, 157), Fishing Net (A3 143), Poké Ball (P-A 002; A2b 111), and Shaymin (A2a 069, 081). There are four cards with anti-Basic Pokémon effects: Araquanid (A3 053), Pokémon Flute (A1a 064), Repel (A3a 064), and Victreebel (A1 020). While not an explicitly anti-Basic effect, Lana (A3 152, 194) is directly connected to Araquanid in use, so I would be remiss to not mention it as well.
Celestic Town Elder is a Supporter that lets you add a random Basic Pokémon from your discard pile to your hand. Fishing Net is an Item card with the same effect except it the Basic it grabs can only be a (W) Type. Combee has a (G) Type Basic Pokémon, with an attack for (C) that puts one random Basic Pokémon from your deck onto your Bench. Poké Ball is an Item card with a similar effect, adding a random Basic Pokémon from your deck to your hand, as opposed to your Bench.
Shaymin is a (C) Type Basic Pokémon, with an Ability that works while it is on your Bench. This Ability reduces the Retreat Cost of your Basic Pokémon that are also in play by (C). The wording means a specific copy of this Shaymin cannot reduce its own Retreat Cost. It can affect another Shaymin – whether it’s this version or another – that is Active. If you have two copies of this Shaymin in play, on your Bench, their Abilities will stack and reduce the Retreat Costs of your Basics by (C)(C).
Araquanid is a (W) Type, Stage 1 Pokémon with a three Energy attack that does 60 damage, plus another 60 (so 120 damage total) if the opponent’s Active is a Basic Pokémon. Lana is a Supporter. Her effect states you may only use her if you have a card named “Araquanid” in play. Lana lets you switch one of your opponent’s Benched Pokémon with their Active. This simultaneously makes it easier for Araquanid to attack a Basic, but technically gives it a use – via Lana – when facing Evolutions.
Repel is an Item card that forces your opponent to switch their Active, Basic Pokémon with something from their Bench. Pokémon Flute is an Item card that lets you select a Basic Pokémon from your opponent’s discard pile, and put it onto their Bench. Victreebel is a (G) Type, Stage 2 Pokémon. Its Ability states you may only use it while this Victreebel is Active. It lets you switch an opponent’s Benched Basic Pokémon with their Active, once during your turn.
Fossils
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There are five Item cards with an effect that lets them to be put into play as if they were Basic Pokémon: Armor Fossil (A2 145), Dome Fossil (A1 217), Helix Fossil (A1 216), Old Amber (A1 214; A1a 063), and Skull Fossil (A2 144). You cannot use this effect during pre-game setup, however. You also must have an open Bench spot in order to put any of these into play.
While in play, these Item cards keep their names, but count as (C) Type Basic Pokémon with 40 HP. They have no Weakness, no Retreat Cost, no Ability, and no attacks. They cannot retreat. Their text states you can discard them at any time, during your turn. This actually means after you draw, but before you do anything that ends your turn upon resolution (like attacking).
Though they are not a separate Stage of evolution, they are worth mentioning because of their dual nature. None of the Basic support works on Fossils, because the only effect that applies while a Fossil is in play is Shaymin’s Retreat Cost reducing effect. As stated, these cards don’t have a Retreat Cost, and cannot retreat. When a Fossil is in your deck, your hand, or your discard pile, it no longer counters as a Basic Pokémon.
For the same reason, Pokémon Flute cannot affect them, but Araquanid’s attack, Lana, Repel, and Victreebel’s Ability will all work on a Fossil that is in play. When not in play, Fossils are vulnerable to anti-Item effects. The only two we have so far are Alolan Raticate (A3 107) and Vikavolt (A3 065). Alolan Raticate is a (D) Type Stage 1 with an attack for (D)(D) that does 50 damage, plus discards a random Item from the opponent’s hand. Vikavolt is a (L) Type Stage 2 with an attack for (L)(L) that does 70 damage, and prevents the opposing player from using Item cards during their next turn.
Stage 1
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The normal rules for evolution mean that you cannot put a Stage 1 Pokémon into play without first putting its Basic counterpart into play. You cannot evolve on your first turn, or the turn a Pokémon was put into play. This means it takes one more card and one more turn for a Stage 1 to hit the field than a basic, but one fewer turns and cards than a Stage 2. If the Stage 2 uses Rare Candy, the Stage 1 still requires one fewer cards, but the Stage 2 can hit the field just as quickly.
There are no cards that specifically support or punish Stage 1 Pokémon.
Stage 2
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The normal rules for evolution mean that you cannot put a Stage 2 Pokémon into play with first putting its Basic, then it’s Stage 1, into play first. You cannot evolve during your first turn, nor the first turn a Pokémon was put into play. This means that it requires two more cards and turns than a Basic Pokémon, and one more card and turn than a Stage 1 Pokémon, for a Stage 2 Pokémon to hit the field.
There are two pieces of Stage 2 support: Lillie (A3 155, 197, 209) and Rare Candy. Lillie is a Supporter that has you select one of your injured Stage 2 Pokémon, then heal 60 damage from it (or all damage, if it has less than 60). Rare Candy lets you play a Stage 2 Pokémon onto its corresponding Basic, skipping the Stage 1 form. Other than omitting the Stage 1 form, evolution via Rare Candy follows the normal rules. It does mean that a Stage 2 can hit the field as early as Turn 3 or 4.
There are no Stage 2 specific counters.
Miscellaneous
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For now, there is one card that directly affects evolving, but which doesn’t fall into any of the other categories: Aerodactyl ex (A1a 046, 078, 084; A3a 101). It is a Stage 1 card, and it does evolve from a Fossil, but the important thing about this (F) Type Pokémon is it’s Ability. This Ability works while Aerodactyl ex is in play, and prevents the opposing player from evolving their Active Pokémon. You can still evolve your Benched Pokémon, so it is a very soft lock.