Interestingly, it was originally going to be a GDI vehicle called the "Pulverizer". This probably explains why the shell is capable of destroying burrowed vehicles.
This vehicle is capable of deploying itself onto the battlefield and act as a form of artillery. However, rather than using of conventional long range shells fired at a target location, the Underminer operates by firing burrowing explosive projectiles that drill through the soil and strike enemy positions from below.
This is accomplished at great distances thus preventing the enemy from learning where the attack comes from. They are used primarily for anti-structure operations though they could work equally well against enemy units; furthermore, any burrowing units within the path of the projectiles are capable of colliding with the warheads and being destroyed underground. These vehicles highlight the Brotherhood's new usage of burrowing technology on the battlefield.
One of the uses of the Underminer is anti-structure operations and can be used to clear out a region of any base defenses before sending in the main force into the region. This has the added benefit of preventing the enemy from realizing where the attacks were coming from, thus depriving them of the chance to strike back at the Underminer unit. But unlike the Aftershock, it does not leave a husk behind when destroyed, despite of it's size that it can leave one when killed.
An achievement can be earned if the player uses it to destroy several structures.