Reaper openings can be considered the most common openings for all Terran match ups. While these openings have been well established in Heart of the Swarm and brought over to Legacy of the Void, the new changes in Legacy of the Void have created more variations to this bread and butter opening.

Before I begin, I want to clarify that I conceptually differentiate “opening” and “build order”, and the following discussion is based on this fundamental understanding. What I am discussing in this post is Reaper opening and not Reaper build order.

Changes in Legacy of the Void

Starting worker count

The starting worker count has changed from six to twelve, and it does not only allow you to put down more buildings earlier but it also changes the mineral to gas ratio mined in the early game. Thus, you do not have enough gas to produce Reapers from multuple Barracks if you simply use the build sequence of Heart of the Swarm, even though you can afford to have more Barracks now.

The building time of the Barracks, Refinery and Reaper do not change, so some aspects of the Reaper opening remain the same.

KD8 charge

The new “Reaper bomb” ability provides Reaper with a stronger offensive capability in the early game, and this can snowball quickly in the hands of good players. Thus, it has become more rewarding to produce more Reapers now than in previous expansion, and this is evident in the Reaper openings we see nowadays. More importantly, although the primary role of Reaper is still scouting, it has slowly been shifting from a scouting unit with harassment capability to a harassment unit with scouting capability.

While the new ability makes Reaper stronger, it remains an early game only unit.

Basic one Barracks expand

14 – Supply Depot
16 – Barracks
16 – Refinery

If you build the Refinery on the same supply right after the Barracks, you will have 50 gas for a Reaper when the Barracks completes. This applies in both Heart of the Swarm (12/12) and Legacy of the Void (16/16).

This has been done in all match ups in both Heart of the Swarm and Legacy of the Void. The key discussion points in Heart of the Swarm were the number of Reapers produced, when the Reactor is built and whether the workers are pulled off the Refinery. These have been changed in Legacy of the Void.

Number of Reapers

The number of Reapers varies in match ups because of what the Reapers can accomplish is different. In TvP, Reaper has little to no room for harassment because of Adept and Photon Overcharge from Pylon, so scouting has almost become its sole purpose. Therefore, usually only one Reaper is produced in a one Barracks Reaper opening for TvP. In TvT and TvZ, there is room for harassment potential, which justifies having a second Reaper. I have yet to see the third Reaper being produced in a one Barracks Reaper opening. The third Reaper basically means that you want to do some damage with the Reapers in the early game on top of scouting, and it is much better to have a second Barracks to produce the additional Reaper(s) in Legacy of the Void. I will discuss more about this later.

Reactor

Most of the time, you will build a Reactor with the Barracks after Reaper production, because the resource and production line up better this way (it has already been figured out at the beginning of Heart of the Swarm). You can make a Tech Lab after Reaper production in some less common builds (for example, Cloaked Banshee).

An example with one Reaper expand (I skip the second Refinery),

14 – Supply Depot
16 – Barracks
16 – Refinery
@100% Barracks – Reaper and Orbital Command
@400 mineral – Command Centre
21 – Supply Depot
@100% Reaper – Reactor
@100 gas – Factory
@100% Reactor – Marine x2

The two Reaper expand is the same, but you only build the Reactor after the second Reaper. It is not necessary to produce the two Marines if you are going to swap add on, as the Factory and Reactor should be done at around the same time. The key difference is the trade off of second Reaper for two Marines.

There is a new minor change to the post Reaper production follow up recently. A Marine is produced after a Reaper is produced, and the opening looks like this.

14 – Supply Depot
16 – Barracks
16 – Refinery
@100% Barracks – Reaper and Orbital Command
@400 mineral – Command Centre
21 – Supply Depot
@100% Reaper – Marine
@100 gas – Factory
@100% Marine – Reactor

This is normally used in TvZ, and rationale is quite well thought out. If you only want to make one Reaper for scouting, you will make the Reactor right after the Reaper as I have mentioned above. Then, you will have two Marines, before you switch the Factory on to the Reactor for Hellions. Both the “Reactor first then two Marines” and “one Marine then Reactor” have the same total production cycle time but only differ in sequence (Reaper + Marine + Reactor). The Factory finishes slightly later for the two Marines version, but the Reactor Hellions production time for both are almost identical. Therefore, the only difference is the number of Marines produced and when they are produced. Based on the current understanding, the one Marine version is preferred in TvZ, because the single Marine that is produced earlier can be used to fend off the scouting Overlord earlier. The second Marine is not as valuable as having that one Marine earlier in normal circumstances.

The two Marine variation is better in two situations. One is to move out on the map to hunt an Overlord, and it is usually not successful in my opinion. The other is to have that additional Marine for an attack early on. For example, you want to do a Hellbat, Marine and Medivac attack.

Workers at Refinery

It is unnecessary to pull workers off the Refinery in order to have more mineral for more Barracks or quick third Command Centre because of the mineral to gas mining ratio in Legacy of the Void early game.

Multiple Barracks

Multiple Barracks Reaper openings have been quite popular now, and this is mainly due to the two Legacy of the Void changes I mentioned above.

Double Barracks

14 – Supply Depot
16 – Barracks
16 – Refinery
16 – Barracks

Two Barracks Reaper macro opening is not new, and it has been utilised in Heart of the Swarm occasionally in TvT if the map allows. The “Reaper bomb” really makes a big difference in how much this build can accomplish in the early game.

Alternatively, you can proxy the two Barracks to favor more on dealing damage than transition ease.

Triple Barracks

14 – Supply Depot
15 – Refinery
16 – Barracks
17 – Barracks
18 – Barracks

Three Barracks Reaper opening is relatively extreme, and it can even be considered a cheese. This build is more map dependent compared to single and double Barracks openings. As shown in the vod above, the high number of Reapers can easily get out of hand if Zerg do not react well. If Terran are able to keep the Reapers alive, the high number of Reapers can even kill Roaches and micro against Zerglings with speed.

Build wise, it is important to note that this is a gas first opening because you cannot support three Barracks Reaper production if the Refinery is built after the first Barracks. Legacy of the Void has a strong impact on Terran gas first opening, because the standard first Barracks timing is not delayed after building a Refinery first. This changes the dynamics of how Terran mirror play out in the early game, because the timing of the Barracks usually affects (it affects the timing of the Starport) the respective offender and defender role of TvT.

Gas first tech-heavy

The no delay in the first Barracks timing with gas first opening is obvious when you compare the new build with the old one in Heart of the Swarm. For example, the popular TvT gas first Reaper build in Heart of the Swarm. I have discussed about the Legacy of the Void version before, it looks like this,

14 – Supply Depot
15 – Refinery
16 – Barracks
17 – Refinery
@100% Barracks – Reaper, Orbital Command and Factory
20 – Supply Depot
@100% Reaper – Reaper
@100% – Factory – Hellion and Starport
26 – Supply Depot (build Supply Depot accordingly hereafter)
@100% Reaper – Tech Lab
@100% Hellion – Hellion
Constant Hellion production
@100% Starport – Swap Starport onto Tech Lab for Cloak Banshee or Raven, and Reactor on Barracks

It takes the second Refinery early in order to get Reaper and tech up to Starport at the same time, and the trade off is the relatively late Command Centre. In contrast to the Heart of the Swarm version, the one in Legacy of the Void does not take the defender role by default because the Starport is not delayed based on the offender versus defender role concept.

I believe we have not seen it all yet in regards to some of the possible minor variations for Reaper openings, but the openings in this post should still be relevant for a long time unless there are future patches that change how Reapers work.

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