Wergild is a value placed on a human being. If someone gets killed, and the killing is deemed unjust, or otherwise offends the laws of the victim tribe, then the offending party must pay a wergild. Not paying it usually leads to war.
There are several events where you might need to pay a wergild in order to avoid a feud.
In Orlanthi society, the value of a wergild varies depending on the rank of the individual: