The Stasis Ward is a Protoss unit that is produced from the Oracle. While it traps units for 21 seconds, the units trapped cannot be attacked or affected by abilities. The Protoss player can however use this time to take a favorable army placement.
The Oracle is generally acquired for its Pulsar Beam ability in the early game to harass and its Revelation ability in the late-game to keep tabs on the enemy army, and, as such, Stasis Ward is a niche ability. Stasis wards can be placed in choke points to delay counterattacks and give the defending player ample time to respond. If an enemy moves his army onto a stasis ward, the opposing player can engage into the stasised army and deal with both portions of the army at different times, granting a large advantage. The stasised player will be forced to retreat with the rest of his army and wait for the stasis to wear off, or abandon his forces altogether.
Since oracles are usually made in the lategame for their ability to cast revelation on the enemy army, some stasis wards can be placed. A few stasis wards on an expansion can help the defending player deal with Zealot or Dark Templar run-bys, splitting up the enemy forces into smaller chunks and giving him/her more time to react. Despite the threat of a stasis ward + disruptor combo, stalkers are fairly resistant to them thanks to their ability to evade danger immediately with their Blink ability. The stasis does not offer as much of a window for aggression as in the other matchups, because of how hard it is to engage into an enemy army with Disruptors.
Since Terran bio armies do not usually accompany a mobile detector with their main army, oracles left over from the early game can surprise entire bio forces with a few well placed stasis mines. They are not effective against bio-based harass, however, since Terran harass is most often seen in the form of drops, and the autocast on the stasis mine prevents more than the first units dropped to be caught
Stasis wards can be effective at denying enemy zergling runbys, as a single stasis ward can trap a handful of zerglings, and a zealot warpin can cleanup the rest. A stasis ward can also be placed behind one's natural wall-off. This makes it so if a pack of zerglings does happen to slip past your defenses, it will activate and use the stasised zergling to block the rest from entering, allowing the defending player to react accordingly
|Patch 2.5.1 Balance Update #1|
- Blizzard Entertainment (14 May 2015). "Legacy of the Void Beta Balance Update -- May 14, 2015". Battle.net.