From The Heroes of Might and Magic III wiki

This is a combination artifact.

Combination artifacts were introduced in the expansion Shadow of Death,
and are only available when it is installed.

In addition to the regular bonuses the Statue of Legion gives you +50% creature growth based on the Castle creature generation level for all towns.

Requires the following artifacts to create:

• Head of Legion
• Torso of Legion
• Arms of Legion
• Loins of Legion
• Legs of Legion

You cannot purchase combination artifacts in Artifact Merchants. Cost is derived from sell price.

Basic Cost: 125000 gold