You must spend a minimum of 25% of your points on Core units.

Core units are the heart of your army, the iconic troops who make up the bulk of every warband and warhost. Unlike other types of units, there is no maximum to the proportion of your points that you can spend on Core units.

For every Core unit with the Expendable special rule in your army, you are required to include at least one other Core Unit without the Expendable rule.