Idea For A Monster In Doctor Who

A Creature That You Only See In The Corner Of Your Eye. When You Try To Look At It, It Vanishes, Im Imagining they never fully show the creature but maybe some close ups like a huge mouth with long tounge, bulging eyes and long lanky hands with huge claws, There Just Hunters, They Aint Smart Like The Master Or Daleks, They Just Go around The Planet Finding Food. Im thinking that when the doctor finds them, he doesn't know all about them but knows some key facts, And Doesnt End up winning just fleeing since its a deserted plant and they are starving. I dont have a name tho. Any thoughts of chances or something?