Malbeth was a Dunadan presumably, aka Malbeth the
Seer. He made
prophecies concerning the return of the King.
Reference: Return of the King, Book 5 of LotR
Malbeth's prophecy of the return of the High King
is quoted in the article Oathbreakers.
Malbeth's prophecy concerning Last-king Arvedui is quoted under Kings of Arthedain and referred to in Arvedui.