All Items your Heroes collect and Crafters craft are displayed here. You start with 16 Slots and can purchase 80 more for a total of 96 Slots. It costs 537,400 coins to purchase every Inventory Slot. With In App Purchases you can purchase an additional 64 Slots for $0.99 USD for 16 at a time. This brings the total number of Inventory Slots to 160. You are given two of each Tier 1 base Material to start the game.

Icon-mdpiThe following is based on The Frozen Tome Expansion and contains spoilers.

After purchasing the Frozen Tome expansion you are given an additional 16 Inventory Slots for free. Another 16 Slots are then available for purchase. It costs 440000 coins to purchase every additional Inventory Slot. This brings the total number of Inventory Slots to 192.

Icon-mdpiEnd of information based on The Frozen Tome Expansion.

Items are sorted, by default, by ID and displayed Potions first followed by Equipment and finally Materials. You can now sort the Inventory by Type, Value, Level, or Rarity. There is no reachable limit to how high a stack of items can go. Pressing and holding a stack will display the number of Materials of each Grade.