In The Vessel, Lucifer has some demons empty out his crypts of weapons in hopes of finding something to use against Amara. Lucifer's Spear is one of the weapons, but he determines that it and the other weapons won't be enough to defeat Amara. While taunting Crowley, Lucifer uses the point of the spear against him.
In We Happy Few, Lucifer arms himself with the spear as part of their plan to defeat Amara with a sequential attack. After the witches use a spell against Amara followed by a mass smiting from the angels and a mass attack from demons, Lucifer stabs the weakened Amara through the back with his spear, bringing her to her knees. Lucifer ceases his attack on God's orders, but when Amara fatally attacks God, Lucifer charges again with his spear to save his father. Amara flings Lucifer against a pillar, causing him to drop the spear before exorcising him from Castiel. It is unknown what happened to the spear afterwards.
The spear has a golden blade and wooden handle. It's engraved with Enochian runes and motifs, but their purpose is unknown.