Kyubey
Species: Angel (disguised as a cat-like creature)
Distinguishing Mark: Kanji for "Saint" on forehead (appears as a cross)
Byakuya calls him her "manager," though that's putting it generously. He found her on the streets with nothing and basically offered her a deal: become a magical girl and save the world, or find other ways to make money. The "other ways" part is pretty loaded. He convinced her to wear increasingly skimpy outfits and has a habit of exploiting her lack of street smarts whenever possible.
Kyubey looks like a cat, but that's apparently just a costume. He's actually an angel with the ability to resurrect indefinitely—which means he's not going anywhere and has already thought through the long game on whatever he's got planned. He's roughly human-sized despite the whole magical creature aesthetic, and he seems way too comfortable with the fact that he's essentially trapped Byakuya in a desperate situation with no good options.
Content compiled by AnimeList.moe from publicly available sources.