Eurybus Valinus was the older brother of Ramasus Ei Valinus and a member of the Time Lord Alliance. Both Eurybus and his younger brother were created by the mad scientist Demacrex, the only clones to survive out of 66. After Demacrex was executed for his crimes, both Eurybus and Ramasus were adopted by The Wordsmith, who Eurybus clashed with because of differences in their personalities.
Always the rebellious one, after the Time War, Eurybus' mental state continued to deteriorate and, upon the revelation that he was connected to the demonic dimension of Deroth, Eurybus seemingly embraced his dark destiny by attempting to kill his brother for rulership of Deroth and its inhabitants. Eurybus would later go on to redeem himself.
After what he thought was a final death, Eurybus was resurrected to be used as a pawn by the mutant Gallifreyan, The Wanderer. With the help of the Alliance, Eurybus was allowed to be put to rest, where he reunited with his estranged brother in the afterlife.
His designation with the T.A. was the less than flattering "The Asshole", although he wore it like a badge of honor. He was referred to as "The Hated" on Deroth.