By Galen Andress
The Sentry is one of the most important units in the Protoss arsenal. Sentries are often the deciding factor in whether you win or lose a battle, and finding a balance in your economy to fit in enough Sentries without delaying your tech for too long is a challenge that Protoss players face in just about every matchup. While you might be familiar with the Sentries’ abilities, you might not be using them to their fullest potential. Learn exactly what to do with your sentries and when, and you’ll be amazed by what it does to your game—and your win/loss record.
Forcefield
Mana Cost: 50
Research Cost: None
Research Time: None
Forcefield is the most commonly used—and most important—spell the Sentry has. Good Forcefield placement is an essential part of Protoss play at all stages of the game, as Gateway units without Forcefield support can be overwhelmed quite easily by enemy ground armies. But it isn’t enough to just throw down Forcefields willy-nilly and just hope for the best; placement is key, and depends greatly on the terrain and the composition of both your army and the army of your opponent. Let's take a look at a few different Forcefield techniques that will help you at all stages of the game.
Ramp Blocking
Ramp blocking with Forcefield is very important for early defense if you are light on units, and can also be used on the offensive to prevent your enemy from reinforcing.
When blocking your ramp defensively, make sure to place your Forcefield as close to the bottom of the ramp as possible. If your Forcefield is placed too high up the ramp, your enemy can gain vision into your base and will be able to attack you, possible picking off the remaining Sentries you need to continue to block your ramp.
When ramp blocking on the offensive, your Forcefields don't need to be quite as precise. Just make sure the ramp is completely blocked so that no units can leak through and you're in good shape.
Trapping an Army
When you have a good amount of Zealots in your army, creating a wall of Forcefields behind the enemy army to trap them is a great way to make sure your Zealots won't get kited and can do maximum damage.
When attempting to trap an army with Forcefields, try and create a cup shape around it rather than just making a straight line of Forcefields. By doing so you'll leave few, if any, escape paths and your Zealots can get up close and personal. This technique is most commonly used against Terran players, as Marines and Marauders can kite Zealots very effectively.
Walling an Army
If your army has greater range than your opponents, take advantage of it. Creating a wall of Forcefields in front of your army will allow your units to fire without taking any damage. This is especially important and effective when using a Collosus-based army, as your Collosi can be completely protected from enemy ground armies while dealing huge amounts of damage from behind the wall. This technique is especially effective against Roach/Zergling based Zerg armies.
In the later stages of the game, your opponent will likely get air units to try and counter your Collosi. Walling your opponent is even more important at this point, as you can create a wall to force the ground army back while falling back and focusing down the anti-air support with your Stalkers.
Splitting an Army
In the later stages of the game, when two large armies are clashing, using Forcefields to split your opponent's army in half is a great way to swing a battle in your favor. By splitting an army in half, you push the back half of their army out of range of the fight, while at the same time trapping the front half and preventing it from retreating.
Guardian Shield
Mana Cost: 75
Research Cost: None
Research Time: None
Guardian Shield creates an aura around your units that gives them an additional 2 armor against ranged attacks. Guardian shield is especially effective against units with a high rate of fire and lower damage, such as Marines and Hydralisks.
When engaging an army with plenty of ranged units, make sure to throw up your Guardian Shield immediately as you start to engage. If you feel confident in your micro abilities, try to individually select a Sentry in the middle of your army to get maximum coverage with your Guardian Shield. Also, try to keep your army under the shield for its entire duration. Zealots with Charge are notorious for blasting ahead of your army and losing the protection of the shield, so try and keep them back to make sure you're getting the most out of your spellcasting.
So, just how big of a difference can Guardian Shield make? Here's an example: a Marine with no attack upgrades only does 3 damage to Zealots and Stalkers under Guardian Shield instead of 5, once it gets past the shields and is hitting the armor. This is a 40% reduction in damage—in other words, it makes an attacking force of 10 marines feel like 6. That kind of shift in damage output can completely change the outcome of a battle, so make sure you're on top of casting your Guardian Shields before every fight against ranged units.
Hallucination
Mana Cost: 100
Research Cost: 100 Minerals, 100 Gas
Research Time: 80 Seconds
Hallucination is one of the most interesting and versatile spells in the game. It creates a fake unit that you can use in a variety of different ways, depending on what you Hallucinate and when you do it. Hallucinated units last for 60 seconds and take double damage, do not deal any damage, and can be spotted by Detectors.
Scouting with Hallucination
By Hallucinating a Phoenix or two, you can get a very good scout on your opponent. Hallucinated Phoenix are just as fast as their real counterparts, so you can do an excellent flyover of your opponent's base and/or army, giving you tons of intel and allowing you to prepare for what your opponent is doing.
Using Hallucinations as Meat Shields
By Hallucinating a bunch of units and using them to lead your attacks, you can soak up a good amount of damage from your opponent's army. Hallucinated Immortals can be especially effective in this way, as they retain the Hardened Shield ability. Since they are Hallucinations, they reduce attacks to 20 damage instead of 10 with the Hardened Shield, but it can still be a great way to bust Siege Tank lines.
Hallucinating Collosi, Void Rays or High Templar can also be a great way to draw fire away from your real units. Since Collosi and High Templar are high-priority targets for your opponent, you can force them to waste time and spells and make them move out of position to target your fake units.
Using Hallucination for Mind Games
By creating Hallucinations, you can force your opponent to think you're going down one tech path when you're really going down another. For example, Hallucinating Collosi and showing your army to your opponent will force them to react to them, while you in fact are going for High Templar, for example.
To see a great example of Hallucination mind games in action, check out the Related Video section for Idra vs. Huk Game 2 from Pool A in Dallas, where Huk Hallucinated a bunch of Void Rays and tricked Idra into leaving the game.
