Phaerus was a mercenary employed by the Shining Crusade during the events of Baldur's Gate: Siege of Dragonspear. Although he never crossed paths with Gorion's Ward, the Bhaalspawn learned of his existence by speaking to three Crusader guards; Anji, Bardyla, and Spensse, who recounted the tale of how Phaerus once got drunk and accidentally dropped a Potion of Fire Breath into their campfire, resulting in a massive explosion and a cloud of nauseating fumes, much to the anger of Turin Brassbreaker.
By replicating this feat, Gorion's Ward was able to access The Warrens that lay beneath Dragonspear Castle, with Turin openly blaming the chaos on Phaerus as she swept past them.