Greybird

Appearance: He's been described as a huge fluffy grey tabby with green eyes and a battle scared face

In chapter 2 Echoshade recognises him as the cat that kill Mosspaw and Daisykit when Orchidstar found out she told his clan leader and he was exiled. A prequal was confirmed called "Orchidstar's life" he'll presumably appear there.

He's described to have a battle-scarred face in chapter 1 though the scars are never shown in covers only in one drawing.