Loot

Loot is the Equipment and Heroic Deeds found in loot boxes. A loot box will always contain 3 items (an exception is the Bögenhafen Chest), of which at least 1 will always be equipment.

items send to your inventory. If you own too much items in total of 5 heroes (846 or above), you can't open any of Loot Boxes.

it says, "Inventory full. Salvage items to open Spoils of War."

Loot Boxes
Loot boxes are rewarded in a number of ways, which determines the type of the box. Rarity and the maximum Item Power of the gear contained within the box are dependent on the box type. Note that most types of boxes also have a box Tier, which is explained at the bottom.

The game keeps track of the highest Power value you've ever obtained for each Equipment slot (across all Heroes & Careers), even if you Salvage the Equipment. It then calculates the average highest power across all 5 equipment types. New items received from a loot box (or by Crafting) have a power level of this average highest power -5/+10, up to the limit listed above.

Example: If the average Power value of the most powerful item you have found (across all characters and careers) for each slot is 190, any loot box better than a strongbox will give you equipment from 185 to 200 Power. If you find a weapon with Power 200, the next Emperor's Chest you open will give you gear from 195 to 210 Power. However, if you open a Peasants Strongbox it will still give you equipment of Power value 100.

Box Tiers
When completing a Mission, the tier of the obtained loot box will be determined by a system which replaced the dice game from Vermintide 1. Accomplishments made during the mission will give you points (shown by a progress bar). Depending on how many points you score, you are given loot boxes of a higher tier:

Higher tier boxes have an increased chance to give higher Rarity equipment.