There are and have been several bands named Gehenna, the most notorious of which are the following:
These are photos from concerts where Gehenna played, so they may be of other bands that played the concert as well.
Gorgoroth / Kampfar / Gehenna / De Profundis Dec 10, 2015 Bristol, England, United Kingdom Uploaded by Josh King
Hellfest 2014 Jun 20 - 22, 2014 Clisson, Pays de la Loire, France Uploaded by Sheb
