He crowned Aegon against the wishes of King Viserys and spilled the first blood of the war, as he killed Lord Lyman Beesbury, Master of the Coin, during the Small Council meeting when he spoke in favor of Rhaenyra.
He served as one of his closest aides during the war, even rising not only as Lord Commander of the Kingsguard, but as Hand of the King as well, when Aegon dismissed his grandfather Otto Hightower from the office.
Cole and Prince Regent Aemond Targaryen led an army of 4,000 greens from King's Landing to retake Harrenhal in the Riverlands from Prince Daemon Targaryen, who vacated the castle before Criston arrived. After hearing of the Lannisters' defeat in the Battle by the Lakeshore, Aemond began burning the Riverlands and Cole marched his remaining 3,600 greens south along the western shore of the Gods Eye, intending to join with the army of Lord Ormund Hightower. However, the Kingmaker's forces were ambushed by the Winter Wolves and river knights south of the Gods Eye, and he died early in the battle at the stony ridge in 130AC.