When I try to upgrade my destructives, the list is empty. All my destructives are gone. In the game, I go to Inventory/upgrades and under 'current destructive upgrade' I tick on "Click here to find Destructives to Upgrade!" and it's empty. I know that I have many in there but they appear to be gone now.
Destructives are consumable. You use them up when you fight. If you want to upgrade them do it as soon as you're done doing your Outbreaks before you start fighting.
