The man only known as Mastodon was a member of Central Intelligence Agency's Team X in the 1960s, alongside Wolverine, Sabretooth, Maverick, and Kestrel.
He took part in a mission in Cuba against former Team X member Silver Fox, who had betrayed the C.I.A. and was then known as Zora de Plata.
He was at Berlin, Germany with other members of Team X when they battled Omega Red and obtained the Carbonadium.
He appeared for the first time in the present day as an old man, dying in the arms of Jubilation Lee from old age.