Onix

Underground, and at 80 kilometres per hour. Onix drills through the ground by spinning and twisting its body as it searches for food, and the tunnels it leaves behind don't stay empty: two Pokédex entries say that Diglett use them as homes. It eats by burrowing, literally. It absorbs everything it finds in its path, and —the same text says— that is what makes its body so solid.

That body is 8.8 metres long and weighs 210 kilograms: a chain of grey rocks with a horn on its head and segments that taper towards the tail. The official category, Rock Snake Pokémon, describes the silhouette well and falls short on the strangest detail in the entry, which is anatomical: it has a magnet in its brain and uses it as a compass so it doesn't lose its way while digging. Over the years, its body becomes rounder and smoother, so an old specimen can be told from a young one by the finish of its stones.

It has no pre-evolution or alternate form; the Pokédex only records one. It is the start of a line that ends in Steelix, lives in caves, and wild specimens often carry a Hard Stone.

385 base stat points, with 160 of them in a single slot. That Defense is the highest of any Pokémon that can still evolve. The problem is right next to it: 35 HP. A huge Defense mounted on a tiny HP pool delivers quite a bit less than the number promises, and there is nothing to patch the hole on the special side, because Special Defense stays at 45. A medium-power, neutral-type special attack is enough to take it down.

The rest of the sheet doesn't help either. With 45 Attack, the strong moves it learns are just decoration: High Horsepower at level 34 and Iron Tail at 43, with 95 and 100 power that land without any weight behind them. Its 30 Special Attack rules out the opposite route. Only its 70 Speed is left stranded in the middle.

Sturdy is what keeps it standing: from full HP, it can't be knocked out in one hit. Rock Head, its other ability, does nothing unless it is taught a recoil move, and there aren't any in its level-up list. Weak Armor, its hidden ability, is a nuisance — every physical hit it takes lowers precisely the only thing it has.

Rock and Ground give it an immunity to Electric, resistances to Normal, Fire, Flying and Rock, and quarter damage from Poison. The bill comes to six weaknesses, with Water and Grass dealing four times the damage. Its place is in a normal playthrough and in support roles: Stealth Rock at level 25 doesn't depend on any stat, and Rock Slide at 18 arrives early and asks for nothing. Against a physical Normal- or Flying-type opponent, it can survive the turn it needs. Against just any Squirtle, not even that.

It belongs to a single Egg Group, Mineral, the catch-all category for stone and metal creatures, which limits the list of possible partners quite a bit. The sex ratio is even, 50% female, so breeding doesn't depend on finding a rare specimen. Its 25 incubation cycles come to about 6630 steps, putting it among the longer stretches in the game. It has no recorded Egg Moves: what one Onix passes to another is what it already learns by level.

Evolution doesn't happen on its own no matter how far it levels up. It has to be traded while holding a Metal Coat, the classic condition since Generation II; in Pokémon Legends: Arceus, the item is used directly from the satchel and the trade is no longer necessary. That is the only route, and it explains why so many people have finished the game with an Onix they never saw turn into anything.

Its habitat is the cave. Its catch rate is 45, the same difficulty tier as a starter: it won't go into a Poké Ball on the first try, and lowering its HP first is a good idea. Defeating it gives 1 Defense EV and only 77 base experience, a small figure for an 8.8-metre creature. It grows at the Medium Slow rate and starts with 70 base friendship.