Complex sentence: Dáin was a descendant of Grór, the youngest son of Dáin I of Durin's folk, and was lord of the Dwarves of the Iron Hills in Wilderland he would go onto be a wise king and one of their greatest warriors.
Split into simpler sentences: Dáin was a descendant of Grór, the youngest son of Dáin I of Durin's folk, and was lord of the Dwarves of the Iron Hills in Wilderland. He would go on to be a wise king and one of their greatest warriors.