It sounds it's essentially an imitation of Sean Connery's voice, with a metallic effect added to it.
You can check out this guy's imitation of the Bane voice:
My Deluxe Ultra Voice Changer app has a 'Metallic' voice, so if you can do a Sean Connery imitation, you might be able to use the Deluxe Ultra Voice Changer, selecting the Metallic option, to emulate a Bane Voice. On Google Play, you have a 15 minute refund window if you decide it's not what you're looking for.