Strength

From NecroWiki

Strength is a measure of a character's raw physical power. For each point of strength, the average damage a player does per hit in melee combat is increased by 0.25. Strength also allows players to wield heavy weapons. Players cannot wield weapons that have a weight heavier than their strength level. Strength also controls the maximum weight a character may wear, wield and carry in their inventory.

Strength can be gained by training the attribute or wearing equipment that grants bonuses to it.

Source(s): Strength help file.