A branch of the powerful Uí Neill clan, with their power base in the city of Donegal.  The current head, Domhnall Mór mac Eicnechain, is king of Tir Chonaill, which comprises roughly the western third of Ulster.  The Ui Domhnaill have many allies among the other clans in Tir Chonaill, in neighboring Tír Eóghain, and elsewhere in Ireland.  They also command a small army of well-trained and well-equipped foreign mercenaries called the gallóglaigh.