The Crovan dynasty may have reached its zenith during Rǫgnvaldr's reign. Acclaimed in one near contemporary Scandinavian source as "the greatest warrior in the western lands", he lent military aid to William I, King of Scotland against the disaffected Haraldr Maddaðarson, Earl of Orkney and Caithness, and occupied Caithness for a short period of time at about the turn of the thirteenth century. Like his predecessors, Rǫgnvaldr was closely associated with the rulers of northern Wales. A daughter of his was betrothed to Rhodri ab Owain, a dynast of the ruling family of Gwynedd. In 1193, Rǫgnvaldr lent military aid to Rhodri against his rivals. Rǫgnvaldr was also involved in Irish affairs, as he was the brother-in-law of John de Courcy, one of the most powerful of the incoming Englishmen. With Courcy's eventual fall from power in the first decade of the thirteenth century, Rǫgnvaldr aided him in an unsuccessful attack on Courcy's rivals.