Marach was lord of the Third House of the Edain when they crossed the Blue Mountains into Beleriand during the First Age. The Third House is therefore often called 'the House of Marach'. The people of his kin were numerous, and Bëor described them as warlike, marching in ordered companies; and the Green Elves did not hinder their arrival in Ossiriand. The Houses of Bëor and Marach spoke a very similar language, which would eventually become the Adûnaic tongue of Numenor Marach settled with many of his people at Estolad, and died at the age of 94 - one year more than Bëor the Old. He had two sons Malach the eldest and Imlach. 

His son and heir was Malach Aradan.