Hillin's familial origins trace back to the commune of Falmagne near Dinant in Wallonia, now in the province of Namur in Belgium, but then part of the Prince-Bishopric of Liège.

After Adrian's death on 1 September 1159 amid rising tensions between the Imperial and Papal parties, Hillin lent his support in the disputed papal election to Barbarossa and his antipope Victor IV rather than to the majority-elected "Sicilian" candidate, Pope Alexander III; Victor made him legate for his support.

In contrast to his predecessor Albero, Hillin was peaceable and prudent in character, as he displayed in continual efforts to establish peace among his various warring neighbors.

In order to settle affairs in the archdiocese, the archbishop turned to Bernard of Clairvaux, with whom he corresponded and to whom he made a personal visit in Lorraine, where the two managed to allay the strife between the people of Metz and Verdun.

In 1169 Hillin engaged in correspondence with Hildegard of Bingen, whom he approached for advice, who visited Trier under his auspices, and who preached a stern sermon to the clergy and people thereof.

Among his secular constructions, Hillin fortified the castles of Manderscheid and Dreis with towers; around 1160, he took to renovating the Ehrenbreitstein Fortress, augmenting the archiepiscopal palace, deepening the moat, laying the foundations of a pentagonal keep, and digging a cistern.