Mortimer was a mutant outcast until Magneto invited him to join his quest for mutant rights. As the Toad, Mortimer became an integral piece of Magneto's Brotherhood and he was right by Magneto's side during all of the greatest mutant victories, including the final battle in Central Park which led to mutant supremacy.
After the triumph of Magneto, the Toad was asked to join the mutant-run S.H.I.E.L.D. He has served admirably under the command of Wolverine in the Red Guard. Recently, Mortimer completed a book detailing the early days of Magneto's triumphant rebellion for mutant rights.