Rook became infamous during a particularly brutal siege, where Megatron and his troops were cornered in a abandoned outpost on the far side of Cybertron's Mithril Sea. He entered the fortress and convinced Megatron to work out a temporary withdrawal from the region. The irony of the situation was he had already convinced Optimus Prime of the very same thing! After a tense stalemate, both sides withdrew from the warzone and refocused their resources elsewhere during the war. Later still, he reported on an attack in Altihex.