An allied contingent is effectively a miniature army in its own right. Accordingly, an allied contingent must abide by the army composition rules and the percentages given for the army composition list used to create it:

Points Limit

An allied contingent must fall within the percentage of points allowed for allies given in the army composition list used to create the army as a whole. For example, the most you could spend on an allied contingent within a 2,000 points army would be 500 points (25% of 2,000 points).

The Allied General

An allied contingent must include at least one character to act as its General.

Number of Units

An allied contingent must include a minimum of one non-character unit. There is no upper limit to how many units it can include.