Marcus (War)

Card art was done by Ian J and webrunner.
You don't get to choose which opponent's slot Marcus goes into. He automatically goes into the opponent's leftmost empty monster slot when you use the ability.
Marcus can't be sacrificed, making the usual avenues of getting rid of him either destruction in combat, or using his ability to return him to the opponent.
Even if the opponent doesn't use light or grey monsters, Marcus has stats of a typical 5 beatstick anyway.
If he can be combo'd with turn-skipping spells or abilities such as Time Machine or Trinary Black Hole he can do massive amounts of damage, usually wiping the field of the opponent's nondark monsters before they can a chance to play again.

Card History

Jul 30th, 2005: Card released in War of the Webcomics.
Aug 21st, 2005: Card given a failure cost of 4.
Mar 1st, 2007: Card fixed to have its modifier move into the new monster slot, instead of disappearing.
Sep 9th, 2007: Details in forum post
Oct 8th, 2007: Gained Can't be sacrificed.
Jan 4th, 2008: Details in forum post
May 18th, 2008: Details in forum post
Jul 11th, 2008: Details in forum post
Sep 21st, 2008: Monster type changed to alien infiltrator from infiltrator.
Jun 10th, 2011: Monster type changed to alien spy from alien infiltrator.