Teomner was a Nephite military officer under Helaman during the campaign to retake the city of Manti from the Lamanites, around 63 B.C. When the Lamanites prepared to come out against Helaman’s army, Helaman sent Teomner and a small number of men to conceal themselves in the wilderness, along with another officer, Gid, and his men. Gid’s men were on the right and Teomner’s on the left, while Helaman remained with the rest of the army in the camp (Alma 58:16-17).
When the Lamanites came out and were about to attack, Helaman’s men retreated into the wilderness, drawing the Lamanites in pursuit past the hidden positions of Gid and Teomner without being discovered. After the Lamanite army had passed, Gid and Teomner rose from their concealment, cut off the Lamanite spies so they could not return, then fell upon the guards left at the city, destroyed them, and took possession of it. By this means Gid and Teomner regained their strongholds, the Lamanites having led nearly their whole army away into the wilderness (Alma 58:20-23).
The actions of Teomner and Gid are recorded in Helaman’s epistle to Moroni, in which Helaman reports that all the cities taken by the Lamanites in that quarter were again in Nephite possession, though his armies were small to hold so many cities and lands (Alma 58:32-33).