Rognvald Eysteinsson didn't want to be a Scottish Earl, and his brother paid the price for it.
Eysteinsson, a Viking warrior and sailor, helped Harald Finehair subdue various bands of Viking raiders after they rejected Finehair's authority and union under the kingdom of Norway. Eysteinsson's son Ivar was killed while battling the Viking pirates along the Orkney and Shetland islands off the coast of Scotland, and after the islands were taken by Norway, Finehair gave them to Eysteinsson to claim as Earl. Rognvald didn't want them, so he transferred the title and land to his brother Sigurd.
After establishing his earldom, Sigurd allied with the former Viking warlord Thorstein the Red to expand his influence on the Scottish mainland. Together, they conquered all or part of the territories of Caithness, Moray, Sutherland, Argyll, and Ross. In Moray, Sigurd feuded with the local nobleman Máel Brigte, known as Máel Bucktoothed or Máel Tusk because of his protruding buckteeth.
The two men agreed to meet on the field of battle with 40 men each to settle their territorial disputes. Sigurd ignored their deal and tried to sneak 80 men onto the field. Máel Brigte knew he’d been tricked when he saw that each of Sigurd's horses had two men's legs dangling from its flanks, but rode with his men into battle anyway. Máel Brigte and his troops fought fiercely and killed a number of Sigurd’s men, but were eventually all killed themselves.
Sigurd had his men behead their enemies and strap the heads to their saddles as trophies. Sigurd took Máel Brigte's head for himself, and as he rode back to his stronghold, one of Máel Brigte's buckteeth scratched and cut his leg. The wound quickly became infected and the Tusk had his revenge when Sigurd died soon after.