The 11 unknown men, each dressed in black robes and sitting in a line, were spotted making strange synchronized gestures during the league match, which Bayern won 3-2.
Situated six rows from the pitch just beside the halfway line in the stand opposite the broadcasting gantry, the group was also seen by TV viewers all across the world.
One fan, Torsten Schmidt, said: "It was very weird. They sat very still for a long time but then would hold their hands up together, or stand up in unison and then sit down again. Everyone near me was very confused. Some people laughed, some looked astonished. It was just very weird."
A key feature of their clothing was a circular symbol on the chest of their robes. It clearly resembled the logo spotted at a series of linked unexplained event over the past week.
The same symbol has been seen at locations across the globe, starting with the appearance of a hologram on Rio de Janeiro's Sugarloaf mountain on Sunday, 20 October.
A three-meter football displaying the sign then gouged a huge hole in the turf at London's amateur football hub Hackney Marshes 24 hours later, while New York City's Times Square was struck by similar images on the tourist spot's world famous digital billboards.
Further sightings of the symbol have been witnessed in the Copacabana neighborhood of Rio and on the Brazilian city's Santa Marta hill, but this is the first time that the mystery has spread to a professional football arena. Also repeatedly spotted at the locations has been the message: #WINNERTAKESEARTH