Mega Steelix ex Deck Guide in Pokémon TCG Pocket

The Mega Steelix ex deck is a defensive Metal Metal archetype that evolves Onix into a 220 HP attacker whose Adamantine Rolling both deals 120 damage and hardens it against the counterattack. A thick package of Tools and healing forces opponents to spend three or four turns breaking through a single Pokémon. This slow, deliberate deck wins by making each of your knockouts cheaper than each of theirs.

The decklist

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Deck Breakdown

Pokémon6

Basic2

Evolution4

Trainer14

Item6

Supporter4

Tool4

Total20

Opening Hand Probabilities

Possible StarterForced Starter

Onix A1 #150

100.00%

100.00%

How it works

Mega Steelix ex is a Stage 1 that evolves directly from Onix, and it is the entire game plan. For Metal, Colorless, Adamantine Rolling deals 120 damage, and during your opponent's next turn Mega Steelix ex takes 20 less damage from attacks and has no Weakness. That rider is huge: a Fire Fire attacker that would normally hit its Weakness for an extra 20 instead deals 20 less than printed, a swing of 40 damage. Remember the risk: a Mega Pokémon ex gives up 3 points when Knocked Out, which hands over the game on the spot.

Onix is the lone Basic and the foundation every game is built on. It is a Fighting Fighting type with 110 HP, and its Land Crush attack costs Fighting, which a Metal Metal Energy Zone will never pay, so treat Onix as a body that soaks hits rather than an attacker. Each Onix evolves into either Steelix or Mega Steelix ex, so one Onix only ever becomes one of the two branches. With just two copies in the deck, keeping both alive long enough to evolve is your first priority.

Steelix is the second branch of the evolution split, a Stage 1 Metal Metal Pokémon with 150 HP that also evolves directly from Onix. Heavy Impact deals a flat 110 damage for Metal, Colorless, only one of which must be Metal Metal Energy. Because it is not a Pokémon ex, it only gives up 1 point when Knocked Out, making it the safer attacker when you are ahead on points or when losing a Mega would end the game.

The Tool suite is what turns big HP totals into genuine walls. Giant Cape grants +20 HP, pushing Mega Steelix ex to 240, while Heavy Helmet is a defensive Tool and Metal Core Barrier reduces damage for your Metal Metal Pokémon. Only one Tool can be attached per Pokémon, so spread them across your line. Potion heals 20 damage a copy, and combined with Adamantine Rolling's damage reduction it forces opponents to find an extra attack they did not budget for.

Matchups

Matchup	Favorability	How to play it
Psychic Psychic ex decks	Favored	Nothing in your line is weak to Psychic Psychic, and Adamantine Rolling's reduction blunts their mid-range numbers. Keep Potion for the turns you cannot attack and let the 240 HP Giant Cape wall trade two of their attacks for one of yours.
Water Water box decks	Even	Their attackers tend to need two hits to break 220 HP, which is exactly the race you want. Use Guzma to strip any defensive Tools they attach and keep Adamantine Rolling active every turn so their math never lines up.
Lightning Lightning tempo decks	Even	They pressure Onix before you can evolve, so use Poké Ball early to bench the second Onix as insurance. Once Mega Steelix ex is online with a Tool attached, their small attackers struggle to finish the job.
Darkness Darkness aggro decks	Unfavored	Fast chip damage punishes your slow setup and four-energy attack costs. Lean on Steelix as the first attacker since it only concedes 1 point, and save Potion to undo their early chip on Onix.
Fire Fire decks	Heavily unfavored	Both Steelix and Mega Steelix ex are weak to Fire Fire, so every hit lands for an extra 20 unless Adamantine Rolling is active. Never skip an attack with Mega Steelix ex, because the no-Weakness rider is the only thing keeping you in the game.

Tech options and swaps

The flex slots are the disruption singles. Guzma discards every Tool attached to each of your opponent's Pokémon, and Field Blower also removes opposing Tools and Stadiums, so against Tool-light decks this coverage is redundant and a second Hiker would add more. Lucky Egg is a card-advantage Tool that competes with your defensive Tools for the one-per-Pokémon slot, making it the first cut in a leaner build. Jasmine is the Metal Metal support Supporter worth keeping in any version, while Pokémon Communication trades a spare evolution for a random Pokémon from the deck and smooths awkward draws.

How to pilot it

1. Set your Energy Zone to Metal Metal only. Adding Fighting Fighting for Land Crush sounds tempting, but random attachments will strand Mega Steelix ex without its two required Metal Metal Energy.
2. Open with Poké Ball, which pulls a random Basic from the deck; since Onix is your only Basic, it always finds the second copy. Get both Onix down early.
3. Going first means no Energy attachment on turn 1 and no evolving, so just bench, attach a Tool if it protects Onix, and pass. Going second, start attaching immediately so the evolution comes online with Energy already banked.
4. From turn 2 onward, evolve the Active Onix. Choose the branch deliberately: Mega Steelix ex when you need the 120 damage and the defensive rider, Steelix when conceding 3 points would lose you the game. No Pokémon can evolve the turn it entered play.
5. Bank one Energy per turn toward the four-attachment cost of Adamantine Rolling, using Professor's Research and Hiker to dig for Tools and the second attacker while you wait.
6. Once attacking, keep the rhythm: Adamantine Rolling every single turn so the damage reduction and Weakness removal never lapse, with Potion patching 20 damage whenever the opponent falls short of a knockout.

The classic misplays: evolving your only Onix into plain Steelix and then drawing the Mega with no Basic left for it, and committing Mega Steelix ex into a losing trade when its Knock Out gives away 3 points. With a retreat cost of Colorless across the whole line, also assume that whatever is Active is staying Active.

Deck strengths

• Mega Steelix ex reaches 240 HP with Giant Cape, among the toughest single targets in the game
• Adamantine Rolling's no-Weakness rider erases the Fire Fire penalty during the opponent's next turn
• Steelix offers a 1-point attacker so you never have to risk 3 points
• Guzma and Field Blower strip opposing Tools, protecting your two-hit knockout math
• Poké Ball always finds Onix, since it is the deck's only Basic

Deck weaknesses

• Only two Onix in the deck; losing both before evolving ends the game plan entirely
• Four Energy attachments before Adamantine Rolling fires means several passive early turns
• Every Knock Out on Mega Steelix ex hands the opponent 3 points and usually the game
• A retreat cost of four across the line leaves no flexibility once a Pokémon is Active
• 120 damage per turn cannot keep up with decks that set up faster and hit harder

Is it worth building?

Build this if you enjoy attrition chess rather than races. The deck asks for patience, precise Tool placement, and honest math about when the Mega is safe to commit, and it rewards all three with games where opponents run out of damage. It sits below the format's pace setters because Fire Fire matchups are brutal and the early turns are slow, but with only six Pokémon slots to collect, it is one of the cheaper walls you can put between yourself and a loss.