Burden
From EHWiki
Burden is a compromise statistic on equipment. Cloth armor has almost no burden (Phase has none), Light armor has moderate amounts (Shade has less, "of the Shadowdancer" has none), and Plate armor has a lot. Similarly, small weapons (like daggers) have low burden, while heavy weapons (such as maces) have very high burden. Higher quality equipment tends to have less burden than their lower quality counterparts and Ethereal weapons have none. Every point of burden above 20 reduces action speed by 1.