Promethium lockboxes drop MoF. The MoF go directly to your currency though and not your inventory like MoR's did. I believe you need to be 101 or 102 CR for them to drop. Though seemingly high standards now due to the max CR being 103, keep in mind this will be much different with T6 actually released. I would be either stocking up on your lockboxes until the DLC is released OR until you are 103 CR or so. Im at 15 MoF right now due to saving lockboxes. Not a bad head start if you are looking for one.
So I have about 6 Marks Of Fury right now. Where exactly can they be used? I went into Themy and there was one vendor but she wasnt selling anything other than sodas?
U gotta go to Gotham under siege. U will end up on a rooftop with a vendor there. (92 item level gear)
Just found out that if you hit 101 then open your lock boxes you still get MoT but if you log out then log back in you will get MoF wasted 5 lock boxes before I thought to try that