Widow mine

"When the time for an ambush arrives, remember that the Zerg aren't the only ones who can go underground. The Widow Mine packs a nasty surprise, and is ideal for perimeter defense as well as tactical ambushes."

- A Dominion Armed Forces blurb for the widow mine.

The widow mine is a terran unit introduced in Heart of the Swarm.

Overview
A support unit, the widow mine is a quadrapedal device that represents the next step in Dominion automated weaponry. It is just under half as tall as a terran wearing CMC armor. It is controlled remotely, piloted into a contested area and then set to activate when enemy units draw near. Once triggered, the widow mine launches a missile designed to explode in a firestorm of shrapnel, eliminating its primary target as well as any foes that might be nearby. These Sentinel missiles are of short range and pack a fragmentation warhead, that delivers superheated shrapnel to the target and the adjacent area on detonation. The missiles are assembled in an automated manufacturing plant located in the 'thorax' of the unit. After numerous friendly fire incidents, widow mines were outfitted with a powerful friend or foe identification system, which is loosely based on the operative algorithms present in all Crucio smart shells. Initially, the system worked as intended, but it didn't take long for casualty rates to rise once again.

If the widow mine sustains crippling damage to any of its systems, an advanced heuristics recovery algorithm quickly begins the process of determining what’s the best course of action to restore operative efficiency. After executing multiple simulated scenarios, the simple onboard AI reroutes power from affected systems and reprograms the unit’s behavioral patterns to either allow it to complete its mission, or return home for repairs.

Mira's Mercs modified widow mines to accommodate additional weaponry and explosives, after a long period of destructive explosive experimentation.

History
The widow mine was inspired by zerg burrowers, and constructed around a modified version of the spider mine pioneered by Victor Kachinsky. Field tests revealed that the burrowing capabilities of the weapon could be improved at a nominal cost. The addition of neosteel carbide tips, and sonic oscillators that allow each leg to vibrate independently at high speeds, significantly reduced burrow times. The enhanced claws have seen much use in "Mine Fighting", a popular (and illegal) sport that pits two of these robots against each other for credits and glory.

Widow mines have been used in diverse scenarios&mdash;perimeter defense, tactical ambushes, and political assassinations. An apocryphal record even attests to a single widow mine killing a corrupt colonial magistrate and his entourage of like-minded officials by destroying the dining room they were in. Upgrades in drilling technology later allowed the widow mine to reduce its burrow time by two-thirds, with the implementation of neosteel carbide tips and sonic oscillators.

Under the reign of Valerian Mengsk, technicians were perplexed by the occasional misfires of the past, and added more protective plating to the widow mines to better contain accidents and protect against unintended injuries.

Dominion marines have been known to pit widow mines against each other in friendly scuffles at the barracks. For the sake of balance, its drilling claws upgrade is disabled for these fights, not to mention its missile launcher.

Versus
Sentinel Missiles is an autocast ability that automatically activates when a widow mine is burrowed, and cannot be turned off unless the widow mine unburrows. This ability causes the widow mine to fire a missile at a target within 5 range, causing 125 damage (+35 vs. shields) and 40 splash damage (+40 vs. shields). The widow mine then spends 40 seconds rearming. This attack damages friendly units, with the exception of allied burrowed widow mines.

Burrowed widow mines are revealed when sentinel missiles are on cooldown.

Activate Mine: The mine takes 3 seconds to burrow, or 1 second after it has received the Drilling Claws upgrade.

While unburrowed, a widow mine's priority is reduced.

The ability is autocast and can be turned on or off in both activated and deactivated modes.

Co-op Missions
Widow mines are usable by Mira Han and Matt Horner in Co-op Missions. They can be built from the assault galleon, and can be upgraded to send out five explosions on death.

Development
The widow mine was previously a suicide unit.

In patch #8, it lost the ability to autoacquire cloaked units.

For Patch 4.0, widow mines were altered to be observable when reloading their sentinel missile, even if still burrowed. This was done to "reduce certain game ending moments" and make cleaning up unattended widow mines easier, while still allowing the widow mine to perform its splash damage role if properly set up with a terran army or used defensively.