Disclaimer: If I owned Pokémon, IVs wouldn't matter because they wouldn't exist. But I don't!
#501 Oshawott
It is unpopular with Trainers because of its melancholy disposition. This sadness stems from the death of its comrades at the hands of fur hunters.
#502 Dewott
A vindictive otter angry at humanity for the destruction of nature. It attacks Trainers on riverbanks with its lethal scalchops.
#503 Samurott
It appears in many large lakes, prompting sonar scans and investigations. However, it always seems to disappear before being conclusively located.
#504 Patrat
It never closes its eyes. It never lets its Trainer of its sight.
#505 Watchog
A stern, disapproving Pokémon that attempts to correct what it feels are flaws in its Trainer's character. If its Trainer does something it perceives as immoral, its eyes glow solid red and it prepares a punishment.
#506 Lilipup
When employed as a watchdog, it fearfully barks at any sudden sound. Desensitized families often do not listen when a real burglar enters their home.
#507 Herdier
It is kept by shepherds to corral their flocks. If trained improperly, it may herd humans instead of Mareep, trapping them in a barn and biting them if they try to leave.
#508 Stoutland
Used to rescue victims lost on snowy mountainsides, it often does no more than bring a bottle of liquor. This comfort provides only the illusion of warmth and the snowbound humans soon die peacefully in the cold.
#509 Purrloin
It will steal from anyone, especially its own Trainer. It will take anything, even vital medications such as insulin.
#510 Liepard
They were kept in ancient tombs as sacred guards against robbers. Without a food supply, they soon died in their sealed prisons.
#511 Pansage
Its leaf is edible but contains large quantities of oxalic acid. It will attack those who speak evil words.
#512 Simisage
Although traditionally viewed as herbivorous, recent observations confirmed that it often eats meat. It kills the evil with its needling thorns.
#513 Pansear
Closely related to humans, it is commonly used in laboratories to test drugs and cosmetics. It attacks those who listen to evil ideas.
#514 Simisear
A highly social and promiscuous species that lives in large groups. It kills the evil with its scorching flames.
#515 Panpour
It can be used as an organic water filter in unclean environments. It attacks those who ignore evil deeds.
#516 Simipour
A semi-aquatic ape adapted to wetland environments, often mistaken for a lizard man or even mermaid. It kills the evil with its drowning water jet.
#517 Munna
After it has eaten a person's dream, it induces a replacement dream with pink smoke. These artificial dreams are powerfully addictive, and caged Munna are sold widely on the black market.
#518 Musharna
Mirages of mist emanate from its forehead, producing ephemeral phantasms. Those who gaze upon these images forever after pine away their lives in longing to catch a glimpse of them again.
#519 Pidove
A highly successful pigeon that has benefitted from proximity to humans since the industrial revolution. It carries parasites that often cause pandemics in major cities.
#520 Tranquill
Tranquill squabs are considered a delicacy worldwide. Hunting dogs are specially trained to catch the defenseless birds and rend them apart.
#521 Unfezant
Males form elaborate bowers in deep thickets to win mates. Fresh skulls are considered the most desirable decorations.
#522 Blitzle
Unlike other equines, it is virtually impossible to train in captivity. It will bite, kick and throw any riders with the intent to kill.
#523 Zebstrika
A vicious zebra believed by certain sects to cause thunder by galloping through the clouds. Many Zebstrika have died after being released in midair by members of these cults.
#524 Roggenrola
An ancient sentry revived from dormancy after an earthquake. Each is inscribed with the same carving, which has been translated as "Always Watching."
#525 Boldore
Parts of its body are cut off to form the blades of war swords. Almost all Boldore Trainers end up eventually selling and dooming theirs for a large sum.