When Our Party examined some magical treasure found in the caverns beneath Tresendar Manor in Phandalin, Ujio sprung out of a magical sword and Mon-Kei out of a magical sack. The two had been suspended in space and time within these objects for five centuries, placed there to spare them as a battle was turning against the Adept they served, a Veteran of the Psychic Wars named Askelon.
The Veterans of the Psychic Wars are a host of displaced heroes and villains seeking to contain and oppose their historic enemies as they continue to seek to raid other worlds and planes of existence. Time can stand still on the Astral Plane, which connects many of these worlds, and it is possible Askelon made his own escape and the warrior and monk could rejoin him, even 500 years later.
On 1-Ches-1492, Ujio released Askelon from the Seeing Sword, using the Ruinstone. Askelon has vowed to take upon himself a quest to find the paired stone and attempt to restore balance to the multiverse (at least as caused by this pair of objects/concepts).