During a showing of "Ride of the Valkyries," several Valkyries were mistakenly summoned. This marked the first known manifestation of Valkyries in modern times. According to tradition, they can be awakened by praise and they won't be satisfied until they carried a hero off to Valhalla, the "hall of the slain." Egon Spengler and Peter Venkman happened to be in the audience during the Valkyries' manifestation. Out of his love for the arts, Spengler volunteered the services of the Ghostbusters, free of charge. Peter Venkman was the Valkyries' chosen hero but they were all trapped when a Ghost Trap was rigged near a skylight, their only exit.
Classification is not stated but it is stated that they are powerful spirits in Norse mythology. Also, the P.K.E. Meter had readings of the entities that were "practically off the scale."
The Valkyries appear to be at least semi-solid entities. They turn into ectoplasmic putty after crashing into physical structures and their mass changed when they entered musical instruments and pipes. When the Ghostbusters sealed the Metropolitan Opera House, the Valkyries couldn't escape.
Based on Norse mythology, they are ladies that would decide who died in battle.
To learn about Valkyries in Norse mythology, go here
It should be noted that the Valkyries have nothing to do with Divas. There was however, ghosts of Opera Ladies appear in Ghostbusters: The Video Game.
The Real Ghostbusters
- "A Fright at the Opera"