Equipment Slot Upgrade
From BlackTalon Wiki
By utilizing upgrade stones, you can further improve your equipment by enhancing its core stats, such as attack, defense and armor. There is a type of upgrade stone for each equipment category, with them being weapons, shields and body armor. Upon succeeding an upgrade, your equipment will have a number modifier next to its name, like this: . The higher that number modifier goes, the harder it is to succeed an upgrade, meaning that at higher upgrade levels it is more likely that you will need to spend more upgrade stones in order to successfully raise the upgrade level. The limit for equipment upgrading is +10.
Below, a chart was designed to better explain this system: