The answer to stopping Unicron/Thomas meets Primus

This is how The answer to stopping Unicron and Thomas meets Primus goes in Thomas' Adventures of Transformers Prime Beast Hunters: Predacons Rising.

Rainbow Dash: How are we suppose to stop Unicron from destroying Primus?

[Meanwhile at Cybertron's core]

Thomas: Primus. I've come back.

Primus: OpThomas. I knew you'd find out that you were a Train-Prime one day.