After Terra exits Merlin's house, he spots the Unversed known as the γ Armor fly past him. He decides to follow the armor to the Reactor.
While that was going on, the α Armor appears in front of Ventus after Dilan and Aeleus forbid him from entering Ansem the Wise's castle. Ventus decided to follow the armor piece which was also heading towards the Reactor.
While that was going on, the β Armor appears near Aqua shortly after she rescues Kairi from a swarm of lesser Unversed with the help of King Mickey. Aqua decided to follow the armor piece all the way to the Reactor as well.
The Trinity Armor
Eventually, Terra, Aqua, and Ventus found themselves in the same room. Shortly after, the three armor pieces assemble to form a powerful Unversed; the Trinity Armor. The trio of friends teamed up with each other to confront this powerful Unversed. After a long battle the three were able to defeat the Trinity Armor.