Mega Evolution — Deep-Dive Reference

01At a glance

Mega Evolution gives a Pokémon access to a second forme during battle. Unlike form changes (Forecast, Stance Change), Mega Evolution is permanent within the battle and can only happen once per team.

02How Mega Evolution works

Mega Evolution requires three things: a Mega-capable Pokémon, the matching Mega Stone held by that Pokémon, and a Key Stone on the trainer (lore — irrelevant in Showdown/Smogon battle). Once those exist, the trainer activates Mega Evolution at the start of a turn.

Mechanically

• Activation: instant at start of turn, costs no turn. The Pokémon Mega-Evolves before its move resolves.
• Held item slot: occupied by the Mega Stone — you cannot also hold Choice Scarf, Life Orb, etc. on a Mega.
• Stat changes: applied immediately. Mega forms have higher BST (typically +100) distributed unevenly across the six stats.
• Ability changes: most Megas get a new ability (Aerilate, Huge Power, Tough Claws, Pixilate, Sheer Force, etc.). The original ability is overwritten.
• Type changes: some Megas gain a new secondary type — Mega Pinsir adds Flying, Mega Charizard X adds Dragon, Mega Garchomp adds Dragon (already), Mega Sceptile adds Dragon.
• Persistence: lasts the rest of the battle; cannot be un-Mega'd. Switching out and back keeps the Pokémon Mega-Evolved.

03The Speed re-roll

The most important and least-understood Mega Evolution mechanic: when a Pokémon Mega-Evolves, the Speed used for that turn's ordering is re-calculated mid-turn after the form change. This let slow Pokémon Mega-Evolve into faster forms and outspeed something they couldn't pre-Mega.

Old behavior (Gen 6 launch)

• Pre-patch: Speed was calculated at start-of-turn BEFORE Mega Evolution applied. Slow base forms got slow turn order.
• Mega-locked at slow Speed: a Pokémon with 50 Speed in base form and 100 Speed in Mega form moved at 50 Speed on the Mega turn (then 100 Speed for subsequent turns).

New behavior (Gen 7 fix)

• Post-patch (Gen 7 onward): Speed is re-rolled after Mega Evolution applies. Mega-Evolved Pokémon moves at its NEW Speed on the Mega turn.
• Slow → fast Mega: a Pokémon with 50 Speed → 100 Speed Mega now outspeeds opponents at 80 Speed on the Mega turn itself.
• Important caveat: priority calculations were already done. The re-roll only re-orders within the same priority bracket.

Practical implication

Pokémon like Garchomp-Mega (108 Speed → 92 Speed, slower) and Salamence-Mega (100 Speed → 120 Speed) interact differently with the re-roll:

• Salamence-Mega Mega-Evolves: starts at 100 Speed, Mega's 120 Speed re-rolls. On the Mega turn, it now outspeeds anything ≤120 Speed in the same priority bracket.
• Garchomp-Mega Mega-Evolves: starts at 108 Speed, Mega's 92 Speed re-rolls. On the Mega turn, it now moves at 92 Speed — actually slower than what it was. This is why Garchomp-Mega rarely Mega-Evolves on the same turn it switches in (you keep the 108 base for the kill).

04Mega Stones — the activation item

Each Mega-capable Pokémon has a unique Mega Stone (e.g. Lucarionite for Lucario, Charizardite Y for Charizard-Y). The Stone occupies the held item slot and cannot be removed during battle.

Mega Stone mechanics

• Specificity: each Mega Stone is locked to its specific Pokémon. Lucarionite on Pikachu does nothing.
• Knock Off / Trick / Switcheroo: cannot remove a Mega Stone from its corresponding Mega-Pokémon — protected at the engine level.
• Trick / Switcheroo to a non-Mega holder: the Mega Stone is treated as a Plate-equivalent (no effect). You cannot "steal" Mega capability.
• Charizardite exception: Charizard has TWO Mega Stones — Charizardite X (Fire/Dragon) and Charizardite Y (still Fire/Flying). Same for Mewtwo (X and Y).

Mega Stones in Smogon competitive

On Showdown / Smogon, Mega Stones are simply selectable as items in the team builder. The lore mechanics (acquiring them in-game, evolving with a Key Stone) are not enforced — battle-only mechanics matter.

05All 48 Mega forms

The 48 Mega forms break down by introduction generation. Gen 6 introduced 30 (XY launch + ORAS). Gen 7 didn't add new Megas — Sun/Moon and USUM kept the existing pool but rebalanced some.

Gen 6 XY Megas (24)

Venusaur-Mega, Charizard-Mega-X, Charizard-Mega-Y, Blastoise-Mega, Alakazam-Mega, Gengar-Mega, Kangaskhan-Mega, Pinsir-Mega, Gyarados-Mega, Aerodactyl-Mega, Mewtwo-Mega-X, Mewtwo-Mega-Y, Ampharos-Mega, Scizor-Mega, Heracross-Mega, Houndoom-Mega, Tyranitar-Mega, Blaziken-Mega, Gardevoir-Mega, Mawile-Mega, Medicham-Mega, Manectric-Mega, Banette-Mega, Absol-Mega, Garchomp-Mega, Lucario-Mega, Abomasnow-Mega.

Gen 6 ORAS Megas (24)

Beedrill-Mega, Pidgeot-Mega, Slowbro-Mega, Steelix-Mega, Sceptile-Mega, Swampert-Mega, Sableye-Mega, Sharpedo-Mega, Camerupt-Mega, Altaria-Mega, Glalie-Mega, Salamence-Mega, Metagross-Mega, Latias-Mega, Latios-Mega, Rayquaza-Mega (no Stone needed — knows Dragon Ascent), Lopunny-Mega, Gallade-Mega, Audino-Mega, Diancie-Mega.

Plus 4 more Megas added across Mythic events (e.g. Latias-Mega, Latios-Mega already in core, with some confusion in counts depending on which forms you count separately). Total commonly cited: 48 Mega forms (counting X/Y splits as separate forms).

06Primal Reversion (Gen 6 ORAS only)

Primal Reversion is technically a separate mechanic from Mega Evolution but uses the same item-slot system. Only two Pokémon can Primal Revert: Kyogre (with Blue Orb) and Groudon (with Red Orb). Their Primal forms set permanent weather (Primordial Sea / Desolate Land) and have raw stats matching the strongest Megas.

Both Primals are banned to Anything Goes in Smogon; legal in VGC. Primal Reversion was removed in Gen 8 alongside Mega Evolution.

07Iconic Megas by gen

Some Megas defined entire formats. The list below covers Megas whose impact was so large that it shaped how the format was played (or banned to higher tiers).

Gen 6 OU defining Megas

Gen 7 OU defining Megas

VGC-defining Megas

08Banlist & competitive impact

Mega Evolution forced Smogon to introduce a bespoke tier above Ubers — Anything Goes — for one specific Pokémon: Mega Rayquaza. This is the only Pokémon to ever earn that distinction.

Banned to Anything Goes

• Rayquaza-Mega — Delta Stream + 180/180 mixed offensive stats + Dragon Ascent. The only Pokémon banned to AG. Cannot use Z-Moves with Dragon Ascent (in Gen 7).
• Kangaskhan-Mega — banned to Ubers in Gen 6 mid-meta. Parental Bond was uncounterable in Singles.

Banned to Ubers

Mega Gengar (trapping), Mega Blaziken (Speed Boost), Mega Salamence (Aerilate + Speed re-roll), Mega Metagross (Tough Claws + raw stats post-Mega), and Mega Lucario (Adaptability + 145 Atk) all reached Ubers via suspect tests. Mega Sceptile, Mega Lopunny, Mega Charizard X/Y, Mega Diancie, and Mega Latias remained OU-legal.

VGC banlist

• VGC 2014: Kangaskhan-Mega legal — defined the format. Sky Drop banned mid-season.
• VGC 2015: Same as 2014, slightly reduced Mega Kangaskhan presence due to the Smogon-style suspect feedback.
• VGC 2016: Mega Rayquaza legal in Restricted format. Defined the year.
• VGC 2017-2018: All Megas legal in Sun/Moon mainline VGC. No Restricteds.
• VGC 2019: Ultra Series allowed up to 2 Restricted Pokémon — Megas competed alongside.
• VGC 2020+: Megas removed entirely — gen 8 doesn't support them.

09Removal in Gen 8

Mega Evolution was retired with the launch of Sword/Shield (November 2019). Mega Stones still appear in Pokémon HOME and the Pokémon are still catchable in Pokémon GO with their Mega forms — but the Mega Evolution mechanic does not function in Gen 8 or later main-series games.

Why Mega was removed

• Game balance: Megas powercrept normal Pokémon. Game Freak chose Dynamax (Gen 8) and Tera (Gen 9) as alternative once-per-battle mechanics that any Pokémon can use.
• Code complexity: 48 Mega forms each with custom stats, abilities, sometimes types. Maintaining + balancing them across each new generation became expensive.
• Item slot conflict: Mega Stones blocked Pokémon from holding Choice items, Life Orb, or hazards-mitigation items. Game Freak shifted to a clean held-item ecosystem with Dynamax (no item lock).

What survived

Mega Pokémon visuals appear in Pokémon HOME as catalogued forms but cannot battle in Mega form in Gen 8/9 games. Pokémon GO kept Mega Evolution as a separate mechanic post-2020 (each Mega has a long charge time and limited battle availability — completely different from main-series Mega).

10Common misconceptions

• "Megas are still legal in Gen 9" — wrong. Mega Stones do nothing in Gen 9. The Pokémon still exist (Mega Charizard X is in HOME), but cannot Mega-Evolve in any Gen 8+ main-series battle.
• "You can hold Choice Scarf AND a Mega Stone" — wrong. Mega Stones occupy the held item slot exclusively.
• "Mega Evolution costs a turn" — wrong. Activation is instant at start-of-turn.
• "Speed re-roll happens for the entire battle" — half right. After Mega-Evolving, Speed is re-calculated for that turn AND for all subsequent turns. The "re-roll" just means it's recalculated mid-turn rather than waiting until the next turn.
• "You can Mega-Evolve twice with two Megas on the team" — wrong. Once per battle per team, regardless of how many Mega-capable Pokémon you bring.
• "Mega Rayquaza needs the Stone" — wrong. Mega Rayquaza Mega-Evolves by knowing Dragon Ascent, no Stone needed. The held item slot is free for Life Orb / Choice Scarf / etc.
• "Knock Off removes the Mega Stone" — wrong. Mega Stones cannot be removed by Knock Off, Trick, Switcheroo, or any other item-stealing mechanic when held by their corresponding Pokémon.

11Where to go from here

Mega Evolution is gen-locked to 6-7 but its impact on the meta of those gens is foundational. Read the era guides for context.

• Gen 6 X/Y Era — Gen 6 Scarlet/Sapphire Era covers the Mega era in full historical detail.
• Gen 7 Sun/Moon Era — Gen 7 Sun/Moon Era covers the last Mega-legal mainline era.
• Speed mechanics — Speed & Priority Mechanics covers the Speed re-roll in the broader Speed-mechanics context.
• Tera (Gen 9 successor) — Terastallization Deep-Dive for the modern equivalent.
• Z-Moves (Gen 7 alternative) — Z-Moves Deep-Dive covers the once-per-battle item-locked alternative from Gen 7.
• Glossary — every term used above is defined in the Competitive Glossary.