Note: This about the fan-made icon. For the enemy, tilted "Marauder" (click here)
Marauder Shields is a fan-made character icon and the unsung hero of Mass Effect 3. He appears right before the player tries to enter the reaper device that will take the player to the Citadel to beat the game. Since the controversy regarding the ending of Mass Effect 3, Marauder Shields has been the center icon of the ending.
It is really unknown on who really created Marauder Shields. It is suggested that the founders of the "Take Back Mass Effect 3" website have created this character for their movement for a better ending to the game.