Encumbrance is the term given to the amount of weight a character (namely, the player's character) is carrying. In the user interface, weight is represented by the symbol. The total weight that a player can carry is governed by the Strength attribute.
How Encumbrance WorksEdit
A character's Encumbrance limit is equal to five times their Strength attribute. Characters are free to carry any amount of weight up to weight limit without penalty, although they will walk/run slower when carrying a lot at once. Any amount beyond the weight limit, however, results in the character becoming "Over-Encumbered".
In Oblivion, when over encumbered, the character is instantly rooted to the spot until the necessary amount of weight is removed.
Raising Your Carry Weight LimitEdit
The easiest immediate solution to becoming over encumbered is to simply drop something heavy. Another, more agreeable permanent solution is to raise the character's Strength score when leveling up. Unlike Health, a character's carry limit does not automatically increase with level.
As a temporary fix, using a Feather spell, a Potion of Feather, or any method of raising your character's Strength, will increase your carry limit. As Feather spells frequently last a very long time, it is entirely possible to re-cast the spell every time it wears out, or to cast a permanent Feather enchantment on an item. However, enchanting your items with Fortify Strength instead appears to provide much better benefits, since the increased Strength provides the character with greatly improved carry weight and significantly increases melee damage. Strength spells are also much more effective; a point of Fortify Strength allows you to carry 5 times more extra loot than a single point of Feather.
As your Heavy Armor and Light Armor skills increase, the impact of your armor's weight upon your total encumbrance is noticeably reduced. However, this weight modification only applies to armor of that type that you are actually wearing.
There are some monsters (such as Zombies and Wraiths) with attacks that can either directly or indirectly lower a character's strength score, thus temporarily lowering the carrying limit of their victim. This is usually a minor concern for "pure" melee characters, but a dire threat to almost every other character archetype. It is advisable for a player to plan ahead for such a possibility, either by preparing spells and items to counter the problem or by scouting for such foes cautiously and ensuring that one has 'spare' carrying capacity available in an emergency.
The Burden spell is the opposite of Feather, increasing a character's encumbrance. Characters can cast Dispel or drink potions with the same effects to remove this effect. Also, characters skills in Alchemy can create effective poison with Burden effects, in order to restrict a target's movement.
Unless an ingredient has one of the encumbrance-related effects (discussed above) as its first effect, the ingredient must be combined with related ingredients via Alchemy to make a potion or poison with that effect.