Praised as a ratling prodigy Mastardo grew up in the depth of the halls of clan Eshin. There he was taught the trades of assassination and speed.
He studied for years under the intent of working his way through the ranks of clan Eshin and becoming a powerful skaven assassin master.
But this was not to be. 6 months before his training was due to finish mastardo befell an accident during a standard training exercise a fellow trainee lost his footing while scaling a wall ahead of Mastardo.
MAstardo was crushed under the torso of the fallen rat. Feared to be a fatally wounded the instructor used a small chunk of warpstone for mastardo to eat.
This act both saved and destroyed mastardo.
The warpstones magikal properties saved mastardo and cured his life threatening injuries.
It also however caused mutation.
An extra arm grew from the base of mastardo's neck over his right shoulder.
Clan Eshin judged this to be to cumbersome and obvious to allow the young assassin to blend into the crowd and perform effectively.
Mastardo was thrown out of clan Eshin, distraught he left his home altogether and travelled to the near by settlement of Cantaris.

The warhorse's had just finshed a game against the Cantaris Colts and had retired to the local tavern before moving on. Head coach Bra Jape noticed a cloaked shadow in the corner with what appeared to be a hump on his back a closer inspection revealed Mastardo.

The Head coach saw the potential of this young assassin and signed him immediately.
Mastardo has been the star of the team ever since leading the scoring so far in the 08 season