Inventory
“We have a big world, and it is essential to understand what to carry to be able to get the maximum profit.— Q&A
The Inventory is a panel that contains all items and currency owned by a Character. Items that aren't Armor, Artifacts, or Weapons have a maximum stack size of 20.
Mechanics
The fraction in the top-left of the inventory represents how full the inventory currently is. To the right of the sort button, there is a count of how much 
Gold the player currently owns.
Sort
Items can be sorted by pressing the double-arrow button in the top left.
Tabs
Inventory items can be separated into different tabs, which contain one type of item per tab.