Bacoun

Appearance:

A bacoun looks like a mundane domesticated pig, but tend to be on the smaller side, they are never huge, nor especially hairy.

Abilities:

Bacoun stats match normal pig stats, they have no exceptional stats, except for intelligence. All bacoun can fluently understand the common language, and can get by with other languages, even weird and obscure ones. A small number of bacoun can also talk, but this is uncommon.

The greatest and most valuable ability of a bacoun is to act as a magic casting aid. If a magic user is in possession of a bacoun, and convinces the creature to help in their magic casting, the spells are treated as being maximized, or by adding up to two spellcaster levels to the spell. Bacoun are magical and they are natural conduits for power.

Some bacoun are especially tuned to a specific school of magic, which gives them the ability to cast spells from this school without need for any components. They are the most adept at divination and scrying, so many wizards who have no aptitude for this will seek out oracular swine for their magical powers.

References

Wilbur, from Charlotte's Web

Hen Wen, the magic pig from The Black Cauldron

Witches turning humans into pigs, Circe from mythology, Bavmorda in Willow, and so on