Cogita

Intro 100 or so years before Red and Blue Sinnoh was originally called Hisui. Hisui was inhabited by a people called the Celesticans, but one the Dimond and Pearl Clans arrived, the Celesticans just vanished. Cogita is a descendant of the Celesticans and doesn't really interact with other people. Cogita is a pretty wise and sweet woman she's probably in her 50s or 40s by the looks of it. She knows a lot about the Sinnoh myths.