Doeg the Edomite
On the day David came to Ahimelech and took the bread of the Presence while fleeing Saul, Doeg the Edomite, the chief of Saul's herdsmen was there, detained before the LORD. (1 Samuel 21:1-7)
When David had fled and was discovered in the forest of Hereth, Saul criticized his men for betraying him under the tamarisk tree on the height of Gibeah, spear in hand. Doeg the Edomite told him, "I saw the son of Jesse coming to Nob, to Ahimelech the son of Ahitub, and he inquired of the LORD for him and gave him provisions and gave him the sword of Goliath the Philistine. When Saul ordered the priests struck down but no one would obey, Saul told Doeg to do turn and strike the priests, and he killed 85 priests that day. And Nob, the city of the priests, he put to the sword, both man and woman, child and infant, ox, donkey, and sheep. (1 Samuel 22:6-19)
Jewish tradition holds Doeg the Edomite was Saul's armor-bearer who refused to kill him in 1 Samuel 31, and that the Amalekite who brings word of Saul's death to David is his son. It is strange Saul had to ask the Amalekite who he was. Also, IDK if he would be considered a "sojourner" or "alien" at that point, even if he was a different ethnicity. (Matthew Henry's Commentary)