The subject of this article originates from non-canonical sources. To find out about what is considered "canon" see LOTR:Canon.
They battle in pairs, and are designed for fighting in tunnels underground. One uses a large tower shield to protect both members of the team and hold off attackers by sealing the corridor using it; the other fights past the shield using a very long spear.
Vault wardens are not mentioned in any of J. R. R. Tolkien's works and were invented solely for The Lord of the Rings Strategy Battle Game.