Shellder

At night, it drills into the seabed with its tongue, crawls into the hole and goes to sleep with its shells closed and its tongue sticking out. During the day, it uses that same tongue to dig through the sand and look for food. It is a bivalve reduced to the bare minimum: a black head with two wide-open eyes tucked inside a purple shell with four spikes.

That shell is all it has. Pokédex entries repeat that it protects it from every kind of attack and that it is only exposed when it opens; clamping down on an opponent forces it to do exactly that, so it saves the manoeuvre for when it has no other choice. The material is described as harder than diamond, and in ancient times it was used to make shields.

Something happens inside that it does not care about at all. Sand that gets between its shells ends up transformed into a pearl, and it spits it out because it gets in the way — hence why wild specimens may be holding Pearl or Big Pearl. The official category, Bivalve Pokémon, makes no attempt to hide where the design comes from.

It is 30 centimetres tall and weighs 4 kilograms, and it is the smaller half of a two-member line that ends in Cloyster.

Its 305 base stat points are distributed in the worst way imaginable. Its 100 Defense is the only respectable figure, followed by 30 HP and 25 Special Defense: any special attack that gets through knocks it out, no matter how weak it is. Its 65 Attack and 45 Special Attack are nothing to fear either, and with 40 Speed it usually moves last.

What justifies its existence is Skill Link, which makes multi-hit moves always hit five times. With Icicle Spear, at 25 power per hit, that is 125 physical Ice-type power per turn, and with Rock Blast it is another 125 Rock-type power. Both come from TMs. Its other Ability, Shell Armor, blocks critical hits, while its Hidden Ability, Overcoat, protects it from powder, sand and hail.

Its pure Water typing leaves it with only two weaknesses, Grass and Electric, and resistances to Fire, Water, Ice and Steel. It does not cover much by itself offensively, although the Ice moves it learns by level — Aurora Beam at 24 and Ice Beam at 40 — cover Grass and Flying types. Shell Smash, at 44, doubles both attacking stats and Speed while halving both defenses: with 30 HP and 25 Special Defense, spending the turn on it is throwing the Pokémon away.

None of this makes it competitive, because everything it can do, Cloyster does with more Defense and much more Speed. Its real niche is in the campaign: it can take physical hits halfway through the adventure, learns Razor Shell at 32 and Hydro Pump at 48, and can set Spikes or Toxic Spikes by TM if someone feels like setting traps before using the stone.

It belongs to a single Egg Group, Water 3, the one for marine invertebrates, which limits breeding options quite a bit. The gender ratio is 50% either way, so breeding does not depend on finding the female or resorting to Ditto.

Its 20 Egg Cycles are equivalent to around 5355 steps. Eggs hatch with Bubble Beam, Water Pulse, Aqua Ring and Life Dew, four Water-type moves that do not change much; Aqua Ring is the only one with any real use, since it restores health every turn and benefits from its 100 Defense.

Evolution has no level or condition: all it takes is using a Water Stone, whenever you choose. It is worth checking the level-up list first, because Ice Beam comes at 40, Shell Smash at 44 and Hydro Pump at 48, and evolving too early means having to recover those moves by another method.

Its habitat is the sea. Its catch rate, 190, is towards the comfortable end of the scale — where 45 marks the difficult ones and 255 those that fall to the first ball — so an ordinary Poké Ball and a little damage are enough. It grows at the Slow experience rate, needs more experience than average for each level, and gives 1 Defense EV when defeated.