Make abillities consume a resource to function

[xorinzor]

Currently it appears the backpack can have it's ability enabled indefinitely without costing anything. This seems pretty overpowered and unbalanced.

I'd recommend implementing a cost for the ability to be enabled, whether that's draining your EXP, consuming items, consuming a fluid from the tank, etc.

This way players would have to at least put in some effort in order to keep benefitting from the backpack ability.