Vulture Spider Mine
Each Terran Vulture is trained with three Spider Mines. Spider Mines cannot be refilled unless done by triggers. Once Spider Mines are placed, players with no vision with the owner of the Spider Mines cannot see the Spider Mines unless a detector is nearby. Spider Mines can attack nearby enemy units even if they don't have vision of them. You can't manually control Spider Mines but they attack any enemy units that come into range of it. Once Spider Mines hit their target, they deal explosive damage to surrounding units.
Non-obvious spells that can affect a Spider Mine
- Defense Matrix
- Ensnare (only if the mine is not burrowed)
- Stasis Field (only if the mine is not burrowed)
- What's surprising is that we can't use Mind Control or Lockdown on them.
How to make a Spider Mine unburrowed in-game
Spider mines created for P12 (neutral) will stay unburrowed in game. Alternatively you can create a pure-sprite if you only want to see the image of an unburrowed mine.
You can also set any player to 'Neutral' in the 'Map Properties' window of SCMDraft to obtain such an effect.
Spider mine attacking
Spider mines are listed as being "detectors", but they do not actually reveal nearby cloaked units (not even ghosts or dark templars). Spider mines attack based on proximity rather than vision, allowing them to attack cloaked units without actually detecting or seeing them -- hence their "detector" status.
One interesting side-effect of this is that spider mines belonging to Players 9-11 will still attack enemies of those players (though no other unit belonging to those players can), because spider mines do not rely on having vision to attack. Unfortunately, since Players 9-11 do not accept AI scripts you can't be their ally (*) so the Spider mines will also attack you and anything else that is nearby.
(*) You and your computer allies can be friends with Players 9-11 through the "Set Alliance Status" AI Script, but the opposite is not true, so that's why the Spider mines will also attack you and your allies.