Rezna is something of a mystery. Radic found the Swinub while wandering through the icy caves of Johto. She was intrigued by the food he was carrying, and after briefly conversing with Chirin sort of, she decided to come with them without a fight.

Rezna, unlike many of Radic's Pokémon, has a tendency to stay quiet. Her oinks don't tend to form as words... they're simply grunts or wordless requests for food, or pain when she's in battle. She doesn't speak or talk to the other Pokémon in her team. Most of Radic's other Pokémon don't know how to deal with her with the notable exception of Chirin, who is very fond of her. The two of them are the best of friends, something which confuses the others since neither of them seem to talk to each other at all.

Because Rezna says so little and spends almost all her time asleep, there's very little that's known about her. She's somewhat unusual among Swinub and Piloswine because of her unusual coloring... Rezna is a silvery-blue, as opposed to brown. This isn't the normal color for a shiny Piloswine, but Radic has chalked it up to individual variations in a Pokémon's color. Although, he's never seen any other Piloswine that look quite like his own...

While she doesn't say much or anything often, Rezna is fiercely, fiercely loyal to her team. She's incredibly hard to rile, as in it takes sustained and notable effort to even get her to react, but she's not afraid to do something about something that's really bothering her. For example, Chopan if he keeps pestering her will end up getting sat on. Thankfully her typing keeps Poe from doing much more than shrieking at her and flying in circles.

Rezna isn't stupid, although it's hard to gauge her intelligence since she's so quiet. She's very obedient in battle... if she's awake. Rezna spends almost all her time asleep, especially when she evolved into a Piloswine, and therefore when Radic throws her out, she's often snoring and won't listen. However, if she's awake, she'll work hard to support her teammates and do her best.

Even if her teammates may irritate her, she will try to protect them, especially Chirin since the two are so close. But apart from that, the others find her hard to read, given as she's usually just a big snoring pile of fur...

In Johto, Rezna knew Take Down, Blizzard, Amnesia, and Powder Snow.

Rezna is in fics where Radic's later Pokémon come into play, mostly Together Forever.