What is "musaylimah"

Musaylimah or Musaylimah bin Ḥabīb was one of a series of people (including his future wife) who claimed prophethood in 7th century Arabia, which is the time of Islamic prophet Muhammad. He is considered by Muslims to be a false prophet, and is always referred to as "the Liar" ( al-Kaḏḏāb). His followers were also very devout.