From Allods Wiki
A bag is a container that can hold items. Unlike other games there is only one bag slot in Allods Online. Because of this factor it makes inventory space a critical factor in planning quests with your character.
However, bags can be upgraded.
List of Bags
Bag of the League/Imperial Rookie
This is the default bag that every character has upon character creation. League characters get a Bag of the League Rookie and Imperial characters get a Bag of the Imperial Rookie. The bags have 18 spaces/slots.
Rough Dragon Hide Backpack
A Rough Dragon Hide Backpackhas 24 spaces/slots. It can be bought in the Item Shop for 400
Dragon Hide Backpack
A Dragon Hide Backpack has 30 spaces/slots. It can be bought in the Item Shop for 925
Enchanted Dragon Hide Backpack
An Enchanted Dragon Hide Backpack has 48 spaces/slots. It can be bought in the Item Shop for 2500
Imbued Dragon Hide Backpack
An Imbued Dragon Hide Backpack has 54 spaces/slots. It is occasionally available through Radiant Strongbox sales. Because of this, it is extremely rare. This is currently the largest bag in the game.
Obtaining Bigger Bags
Bigger bags can be obtained through the Item Shop or rare drops through chests. The bags can be found under the 'Services' tab of the Item Shop.
In a future patch some bags will become tradable to other players and will no longer bind when picked up. Instead they will bind when equipped.