In the Well of All Sparks, Megatronus to Prima: "You know what? I'm tired of Megatron's scraps!"
He takes dark energon to contact Unicron.
Prima: "Wait, where and how did you take..."
Unicron appears: "Oh, we meet again, Megatronus. So, did you reconsider our deal?"
Megatronus: "Only for this time: do you see that grey mech with red optics?" He points to the sort of portal-window where it can be seen Autobots and Decepticons fighting.
Unicron: "So you want me to make him suffer? So, we have some scraplets that can infest his base, some nightmares about his ex Conjunx Endura, ...
Prima: "Megatron and Optimus were not..."
Megatronus: "Co-smic Ru-st!"
Unicron: "What?! Ok, wait! There are other types of torture we can use..."
Megatronus: "GIVE TO MEGATRON COSMIC RUST! GIVE IT TO HIM NOW!!!"