Gyarados

It lays waste to settlements. That is what one Pokédex entry after another keeps repeating: one got so angry that it wiped out a village in a single night and left not a trace behind, and ancient literature already told a similar story. Its fits of rage last for up to a month, and the furious pressure of its blood does not subside until it has burned everything around it. Some say that the places where it appears are doomed to destruction.

The explanation the games themselves give is physiological. When it evolves from Magikarp, its brain cells undergo a structural change, and that is where its savage nature comes from. What remains is a 6.5-metre, 235-kilogram sea serpent with whiskers, a crest and a mouth that takes up half its head; the official category, Atrocious Pokémon, leaves little room for interpretation.

It closes out a two-stage evolutionary line, with nothing beyond it. The contrast with the beginning is half the appeal: the most useless creature you can fish up transforms at level 20 into the one people fear most, with no item or special condition involved. Even so, it is not commonly seen in its natural habitat.

540 points distributed with barely concealed intent: 125 Attack against 60 Special Attack. Its 95 HP and 100 Special Defense let it take weak special hits, its 79 Defense falls short against physical attacks, and 81 Speed gets it nowhere on its own.

That is where Dragon Dance comes in, learned at level 36 and raising Attack and Speed at the same time. A single turn turns that mediocre 81 into enough to outspeed most things, and Intimidate, its standard Ability, is what gives it that turn: it lowers the opposing Pokémon’s Attack as soon as Gyarados comes in, so switching into a physical attacker is almost free. Its Hidden Ability, Moxie, takes a different route — it raises Attack every time Gyarados knocks out a target, without needing to spend a turn setting up.

It has no shortage of physical moves. Waterfall (level 21) and Aqua Tail (level 32) are its two Water-type attacks with STAB, while Crunch (level 24) and Ice Fang (level 8) cover what Water cannot hit, and it can get Earthquake and Raging Fury from TMs. The Flying typing gives it an immunity to Ground, which is half the reason it can take hits.

What holds it back is that same half. Water and Flying make it take four times the damage from Electric: a 90-power Thunderbolt from something like Zapdos knocks it out before it has set anything up. The weakness to Rock does the rest, and its 110-power Hurricane is a special attack, making it useless with 60 in that stat.

It belongs to the Water 2 and Dragon Egg Groups, with a 50% gender ratio, so breeding your own line does not depend on finding the rare female. Its five incubation cycles amount to about 1530 steps: among the fastest eggs there are, which is curious for something that takes so long to become useful. No exclusive Egg Move comes from the egg — the list is empty, and everything it learns comes from leveling up or TMs.

The offspring is always a Magikarp, and that is where the toll begins. Evolution is as simple as reaching level 20, with no stones, items or time- or friendship-based conditions; the problem is getting there, because Magikarp takes little and gives out even less. Gyarados grows at a slow rate, requiring some of the most experience per level, and gives 2 Attack EVs to whoever defeats it.

Its habitat is the water’s edge, which is where it is found in the wild: lakes, coasts, the shore of anything large enough. Its Catch Rate, 45, puts it in the difficult bracket, although in practice almost no one catches it — they fish up the fish and wait.