TvT Lagforce’s Mech Opener

General Overview

This Gas First Reactor Hellion opener is a safe way to open into Mech, utilizing Hellions and Widow Mines to stay safe against any early pressure while you build up your midgame infrastructure.

Build Order

  • 10 – Supply Depot
  • 12 – Refinery
  • 14 – Barracks
  • 17 – @100% Barracks, start Orbital Command, Factory, and Reactor on Barracks
    • Pull all 3 SCVs out of your Refinery
  • 17 – 2 more Supply Depots
  • 22 – @100% Factory, swap off onto Reactor and start Hellion production (up to 4)
    • Send floating Barracks to opponent’s base to scout
  • 25 – @400 Mins, start 2nd Command Center and 2nd Refinery
    • Put 3 SCVs back into the first Refinery as well
  • @100% 3rd/4th Hellions, start Engineering Bay
    • If you suspect your opponent has a Starport, start Widow Mine production
    • If you are sure your opponent does not have a Starport, continue Hellion production
  • @200 Gas, start 2nd Factory and Armory
  • Benchmark: When you start your 2nd Factory and Armory (@6:40ish), you should have 4 Hellions, 2 Widow Mines, and 26 SCVs.
  • @100% Armory, start +1 Vehicle Plating and Tech lab on 2nd Factory
    • Produce 2 Hellions and 1 Siege Tank at a time
  • @100 Gas, start Starport
  • @400 Mins, start 3rd Command Center and 2 more Refineries
  • Benchmark: When you start your 3rd Command Center (@9:10ish), you should have 12 Hellions, 4 Widow Mines, 1 Siege Tank, and around 43 SCVs.


This build has no army production until your first Hellions pop out, so you are somewhat vulnerable to early Reaper attacks.  However, if you can pull SCVs and chase away the first Reaper(s) long enough to swap off your Factory onto the Reactor, you will easily be able to crush the Reapers with your Hellions.

All the rest of your scouting will come from your first 4 Hellions and your floating Barracks.  Use them in combination to poke the front of your opponent’s natural or main ramp, kill naked Marines, and/or run into your opponent’s main and kill all of his SCVs.  If you only see Marines, assume your opponent has a Starport.  Be sure to start one Missile Turret per mineral line and position your Widow Mines defensively in order to deal with a potential Widow Mine Drop or Banshee build coming your way.


This build only transitions into Mech.  Continue your upgrades by starting Blue Flame and +2 Vehicle Armor as you go up to 5 Factories (4 Tech labs, 1 Reactor) and a Starport.  Spend your excess minerals on Hellion runbys, extra Command Centers, and Missile Turrets.

In Mech vs Mech play, you should be focused on out expanding your opponent while you make a heavy Hellbat/Siege Tank/Viking force.  Be sure to constantly produce Vikings so that you do not lose the air battle or to a potential switch into Sky-Terran.

In Mech vs Bio play, you should be focused on holing up your defense with extra Missile Turrets and Sensor Towers as you make a devastating Hellbat/Siege Tank/Medivac army.  You only need enough Vikings to provide vision for your Siege Tanks – focus your efforts on a stronger ground army with more Medivacs for healing your Hellbats than on making an impressive air fleet.  Widow Mines can be placed on common attack paths to help deter Bio runbys too.

Pros and Cons

This build is a strong opener to help newer players transition into Mech.  It is also pretty safe against most early attacks Terran can do because of the early Hellions, Widow Mines, and Engineering bay built into the build.

However, this build is weak against early Banshees because your only defense is Turrets for detection and Widow Mines.  Also, it isn’t as economical a build as a 1rax FE or Reaper FE, but transitions into Mech much more smoothly.

Favorable Maps

This build is viable on every map because your scouting with Hellions is largely unaffected by the geometry of a map.

  • King Sejong Station
  • Overgrowth
  • Catallena
  • Merry Go Round
  • Deadwing
  • Foxtrot Labs
  • Nimbus


Lagforce’s Meching to Masters YouTube Example

Lagforce’s Mech Opener Tutorial Replay vs a Very Easy AI


Lagforce on Reddit