Before we even had time for field trials, the troops had already taken to calling it a "Skulljack", In the simplest of terms, it's a physical interface designed to access the chip implanted in the ADVENT forces' skulls, applied using directed blunt force.
In combat, a soldier equipped with a Skulljack can melee enemies for special results. However, unless you have researched Skullmining, the Skulljack will only work to progress the story. Once researched, a 'Skullmine' action will be available any time a soldier equipped with a Skulljack has an ADVENT soldier in range.
Skullmine is an option to hack any living ADVENT soldier. On a successful hack attempt you will gain either Intel or a Facility Lead (these are fixed options) as selected in the Hack dialog. Failure will deal feedback damage to the user (this is also fixed). Whether the hack attempt is successful or not, the target will be instantly killed. This can be helpful when dealing with tough ADVENT units.
The chance to initiate a Skulljack/Skullmine hack is 70% and is fixed. If the soldier wielding the Skulljack fails to initiate the hack attempt, 2 damage will be dealt to the target, and only one action will be consumed, even if the soldier dashed. This allows for repositioning if things go wrong.
A Skulljack is required twice to progress in story: In the first the Skulljack is used on an ADVENT Officer, and later, on a Codex.
The Skullmining upgrade at the Proving Grounds improves the Hack stat of any soldier carrying a Skulljack by 25 (on normal difficulty). This makes them an ideal item for Specialists.
On Xbox One unable to hack enemies during Advent Retaliation mission.
Mindcontrolled and reanimated enemies cannot have the "Skulljack" used upon it.