Ivysaur

The bulb on its back has stopped being a seed and still isn't a flower: it's a closed bud, green and tightly packed, already weighing heavily on thirteen kilos of animal spread over barely a meter. Pokédex entries insist on the mechanical consequence of that weight. Its legs and torso have thickened to handle the load, and when the bud grows large enough, it loses the ability to stand upright on its hind legs. What was an occasional posture in Bulbasaur no longer exists here: it moves on all fours, full stop.

The rest of its behavior revolves around flowering. It absorbs nutrients, the bud swells, and it starts giving off a sweet aroma that serves as a warning that it's about to open. It also seeks out the sun for longer and longer, to the point that an attentive Trainer can read the evolution before it happens: if it spends the afternoon lying under the light, the bud is at work.

It's still the Seed Pokémon, the same category as the forms above and below it in the line, even though by this point the seed has already been used up. It occupies the middle step between levels 16 and 32, a short stretch that almost nobody deliberately extends.

Its 405 base stat points are divided with a comfortable symmetry: 80 Special Attack, 80 Special Defense, and a physical block that goes nowhere, with 60 HP, 63 Defense, 62 Attack, and 60 Speed. None of that is frightening on its own. What keeps it in circulation is Chlorophyll, its Hidden Ability, which doubles its Speed while the sun is up and turns that 60 into a number that outspeeds much of what moves in the unevolved formats. Overgrow, its regular Ability, only boosts Grass-type attacks when its health is low and rarely decides anything.

The plan is laid out in Smogon analyses for NFE and ZU, and it hasn't changed much: Eviolite to make mediocre defenses respectable, Growth—which it already learns at level 1—to raise both attacking stats at once under the sun, and from there Solar Beam with no charging turn. Giga Drain restores health while it sweeps, Sludge Bomb hits when the sun runs out, and Weather Ball, which becomes Fire-type under the sun, is there for the Steel types that would otherwise stop it cold.

The limitation is obvious. It depends on someone setting up the sun for it, and against Fire types it has no answer: it switches out. Grass and Poison overlap heavily on offense, and its four weaknesses—Fire, Ice, Flying, and Psychic—are among the most widely distributed there are. Priority moves tear it apart halfway through setting up.

It belongs to the Monster and Grass Egg Groups, the line's usual dual membership, which opens up breeding with almost all the starters and half the Grass-type catalogue. The gender ratio is seven males for every female: only 12.5% are female, so any breeding project starts there or with a Ditto. An egg never hatches into an Ivysaur, though, but into a Bulbasaur; anything you want to pass down has to be planned one step lower.

There are four Egg Moves, and all of them deserve a mention: Petal Dance, Ingrain, Curse, and Toxic. The 20 Egg cycles amount to around 5355 steps, a short wait for a starter.

The evolution condition has no trick to it: Bulbasaur levels up to 16 and becomes this, and this one levels up to 32 and becomes Venusaur. No items, no friendship, no time of day. Its growth rate is Medium Slow, the kind that punishes the beginning and pays off later.

Its recorded habitat is grassland, although in practice it rarely appears in the wild and the usual route is to reach it by evolving. Its catch rate, 45, is the same as its previous form's and nearly all starters': difficult without becoming desperate. It yields 1 Special Attack EV and 1 Special Defense EV.