Complex sentence: There, they were received by the Tuatha Dé Danann (ancient tribe who occupied Ireland before the actual Gaelic celts), suddently Breogan got ambushed by the Tuatha Dé Danann, and they managed to kill one of Breogan's sons, Ith.
Split into simpler sentences: There, they were received by the Tuatha Dé Danann (ancient tribe who occupied Ireland before the actual Gaelic celts). Suddently Breogán got ambushed by the Tuatha Dé Danann, and they managed to kill one of Breogan's sons, Ith.