Backpack

Nothing is more embarrassing for an adventurer than to find the big treasure at the end of the quest, and then being unable to take the masses of coins with them due to not having enough storage space or no hand to hold it. And it is downright lethal to go adventuring without carrying equipment.

For these situations, a backpack is very useful. Worn on the back, it not only does not hinder the adventurer's movement in any way, but allows transportation of numerous items without problem. It is therefore absolutely essential for every adventurer to have one, otherwise he or she shouldn't even bother with leaving town. They appear in Ultima VI, Martian Dreams, Ultima Underworld, Ultima VII, Ultima Underworld II and Ultima VII Part Two.

History
Backpacks were first available for purchase in Ultima VI, although during that time they were only used as a way to have extra space to carry more things, since spece in the character inventory was limited. The same went with Martian Dreams. However, starting with Ultima Underworld, having a backpack became critical, even more so than in later games. In the Underworld-titles, this was because otherwise the Avatar could not carry more than 10 items at the same time. Thankfully, they were in both instances supplied with one early on. Starting with Ultima VII, backpacks were freely available for purchase, while strangely enough in Ultima VII Part Two, every character already came equipped with one, thus none were for purchase.

From Ultima VIII onwards, the backpack became part of the interface and could no longer be un-equipped. The same essentially was true in Ultima IX, but here it was entirely possible for the backpack to be taken away due to plot events, severely hampering progress form that point until getting it back.

Trivia

 * In Ultima IX, Blackthorn takes away the Avatar's backpack at one time of the game. The game progress is seriously hindered by this, and once the player gets it back, it has turned into a complete mess. The backpack can also be taken away by the guards in Wrong when arresting the Avatar.
 * From Ultima VII onward, size and mass of an item were important. This was only changed in Ultima IX.
 * The backpack in Ultima IX can hold exactly 20 items, regardless of mass and size. Thus the need for bugs to get more storage space. The backpack, as seen, also holds the journal, spellbook, map and all arrows.