312 is a modron — a geometric construct native to the plane of Mechanus — that ended up stranded on the Material Plane near Thornwood. Its designation serves as its “name,” reflecting the orderly numerical identity all modrons carry.
In 1486 DR, it befriended a young farm boy named Tobbi, who hoped to leave with 312 and become an adventurer. The pair became entangled in a small extraplanar incursion in Thornwood before the Seekers arrived and helped resolve it. Afterward, Tobbi chose to stay with his family rather than depart, and 312 continued on its way.