Domhnall's reign is noted for its tension with the monarchy. King David II irritated Domhnall by residing at Dumbarton on at least 12 occasions between 1341 and 1346. Domhnall was probably one of the happier Scottish magnets when King David and his agent, Malcolm Fleming, Sheriff of Dumbarton, were captured by the English at the Battle of Neville's Cross in 1346.
Domhnall was also faced with the challenge of fending off the aggressive Stewart clan. Having no male heirs, Domhnall is credited with saving the Mormaerdom by marrying off his daughter Margaret to his kinsman Baltar mac Amlaimh, the man usually known today as Walter of Faslane. This act kept the Mormaerdom within the Lennox line, and preserved it in the medium term from Stewart takeover.
Domhnall died in 1365'