Crobat

Its hind legs stopped being legs. They stretched out to form a second pair of wings, and that gives it the one trait that truly sets it apart from any other bat: it flies with four. The Pokédex entries keep coming back to the same thing: silence. It approaches its prey without being noticed, swoops down, and drains all its blood before it can react.

The good detail is how it gets tired. After spending a long time in the air, it beats only the front pair or only the rear pair, alternating between them; all four at once are for short bursts.

It pays dearly for that on the ground. Without legs, it can do nothing but drag itself along, and it rests hanging upside down from a branch. That is where the entries contradict each other: one says it holds on with its hind legs, while another says those legs no longer exist because they became wings.

It is 1.8 meters tall and weighs 75 kilos, large-adult figures for a Bat Pokémon. It completes the line that starts with Zubat and passes through Golbat, and its coloring is the latter's turned inside out: purple takes over, while blue is relegated to the wing membranes.

130 Speed. That is the number everything else revolves around, and among Poison types only Eternatus matches it, and it's a Legendary. The rest of the spread is simply honest: 90 Attack, 85 HP, 80 Defense, and 80 Special Defense, plus a 70 Special Attack that goes to waste. 535 points in total, distributed to move first and take a hit, not to win exchanges through brute force.

The ability that defines it is its Hidden Ability, Infiltrator: its moves ignore Reflect, Light Screen, Safeguard, Mist, and the opponent's Substitute. Against a team built around screens, that turns a mediocre attack into one that actually gets through. Its other ability, Inner Focus, only prevents flinching.

Poison and Flying is a combination it shares with no one outside its own line. Defensively, it works: immune to Ground, takes a quarter damage from Fighting, Grass, and Bug, and resists Poison and Fairy. Offensively, it is poor, because Poison only hits Fairy types hard and Flying keeps running into Steel and Rock everywhere. On top of that, it carries four weaknesses.

Its level-up moves are Cross Poison, 70 power and physical, at level 25, and Leech Life, 80 power, at level 43. Air Slash arrives at level 34 but is special, and with 70 Special Attack there is not much to work with. Hypnosis, at level 6, is the odd card.

What holds it back is that 90 Attack is not enough to take anything down on its own. Smogon placed it in UU from the second through the fifth generation and again in the seventh; in the eighth it dropped to RU, and it remains there in National Dex. It is not available in Scarlet and Violet.

It belongs to a single Egg Group, Flying, and together with its pre-evolutions it is the only Poison type that appears in it. The gender split is perfectly even, with 50% female, so building your own line does not depend on getting lucky with the specimen's sex.

Its 15 Egg Cycles work out to about 4080 steps using the usual calculation, (15+1)×255. That makes it one of the shorter hatches.

Evolution is the tricky part. Zubat evolves into Golbat at level 22, with no extra conditions, but Golbat only becomes Crobat when it levels up with a friendship of 160 or higher. The starting friendship is 70, leaving 90 points to earn by walking around, battling, using candies, or simply not letting it faint. It is a requirement the game does not spell out: a Golbat can stay a Golbat for the entire game without anything indicating that it is missing affection rather than levels.

Its assigned habitat is the cave, which fits a line found by the dozen underground in the Kanto and Johto games. Its 90 catch rate sits in no-man's-land: neither the 45 of Pokémon that are hard to contain nor the 255 of those that drop into the first ball. It grows at the Medium rate.