The Guardian is a standard level screen dimming Battle Card that appears in MegaMan Star Force 2. Once used the Battle Card will summon a murian to guard the square directly in front of MegaMan's position. The murian will remain on the field until attacked or disposed of by other means. If attacked the murian will attack the row in front of and the side panels of the back two rows.
The artwork of the Battle Card as well as the "Guardian" summoned is a murian EM virus, but cannot be gained by defeating a Murian.