The Trinity Sword is as old as the Angels and Demons and almost as powerful.
In times long past, the world was in chaos. Beings of light and shadow began taking forms and fighting for no discernible reason. The planet, Tera, was in its raw form, for the gods were still molding it. Nothing could survive on the surface save the spawning creatures of light and shadow who were at constant war.
The raw form of Tera was covered in expanding oceans and erupting volcanoes that reaped massive destruction on its surface. Hurricanes and Tornadoes, Earthquakes and Tsunamis all rocked the surface of the developing Tera.
Amidst the chaos and war, four beings formed that were different from those of the light and shadow. They were formed of neither light nor shadow, but of the planet and lived in peace with Tera, but could not tolerate the wars of the other creatures and resolved themselves to put an end to it.
They prayed to their mother Tera and asked her for power and resolve. Tera answered by giving each of the four a different strength. One received command of the creatures of light. One received command of the creatures of darkness. One received command of the power within Tera. One received command over the powers of all things physical. Each received a body to represent their new power. The first took the shape of a creature of light. The second took the shape of a creature of darkness. The third kept his form. The fourth grew to towering heights, able to stand over mountains.
The four took their new powers and tried to use them to end the wars, but their efforts were futile. Frustrated, they called again to mother Tera. Tera answered once more with another gift. She took the three with command over creatures of light, creatures of darkness, and the power within Tera and combined their powers. The three took another form that encompassed all three in one physical form, the form of a sword. The fourth armed himself with the sword, and with one swing banished the creatures of darkness and light to separate realms, forming the Angels and Demons, and calmed the surface of Tera, leaving peace for life to develop. The energy necessary for the swing exhausted the fourth being and he fell dead, dropping the sword beside his body. From his corpse sprouted the first tree.
The Angels, seeing the power of the sword, took it for themselves and hid it from the Demons and the rest of the world for fear that it might be used against them once more.