The Barricade is a special unit used in the Mobilising Armies minigame. When used, it prevents incoming armies from moving through it. But be careful, as your armies cannot pass through them either, even if you were the one to place it. The Barricade is only useful in the Hoard level of Mobilising Armies to block your caves from opponents, so only you can revive gold from that cave. Barricades cost 800 Investment Credits.
Many people prefer to use other things in mobilising armies such as the cannon, but if strategically used the barricade can prove to be a valuable asset (Ex. Block off the other player with baricades and use mages and other specials to decimate the other team).