Logos Prime

Logos Prime was known as the mad traitor.

History
According to legend, Logos Prime coveted knowledge, so much so that he stole both the Covenant of Primus and the Quill from Alpha Trion, only to write into it a passage granting him omniscience. Suddenly all-knowing, and yet contained within what was still a mortal form, Logos Prime went mad. Imprisoned by the remaining Thirteen on an unknown world, Logos Prime lost his temporarily-granted omniscience, but remains as mad as ever. He has not been seen since before the Quintesson arrival on Cybertron.