Opposing Force x Skyrim

A Black Mesa Osprey has come down near you. In the HECU weapon box beside the wreck is Corporal Shephard's gear: the Desert Eagle, the pipe wrench and a Shock Roach. Take it, and Race X Shock Troopers teleport in to take it back. From then on Xen portal storms tear open across Skyrim, dropping Pit Drones and Shock Troopers on towns and roads, Black Ops squads hunt you, HECU Marine squads land to fight on your side, and HECU supply crates fall with the rest of Opposing Force's arsenal.

Everything from Opposing Force is the real thing, converted on your PC from your own Half-Life: Opposing Force the first time you play: the models, their textures, every gunshot, alien chatter, radio call and soldier's voice.

What you get

• Opposing Force's full arsenal: Pipe Wrench, Combat Knife, Barnacle grapple, 9mm Pistol, Desert Eagle, .357 Magnum, 9mm SMG with grenades, Shotgun, M249 SAW, M40A1 sniper (zoom), Crossbow, RPG, Tau Cannon (charge shot), Gluon Gun, Shock Roach (recharges), Spore Launcher, Displacer Cannon (fire, or teleport yourself to the crash site), Hand Grenades, Satchel Charges (right click detonates), Laser Tripmines, Snarks and Penguins. Damage is Opposing Force's own.
• Guns that fire like guns: semi-auto, full-auto, buckshot, clips, reloading (G), ammo to find and loot.
• The invasion: the crash site once you're out of the Helgen intro (a message and a quest marker point to the weapon box), the Shock Trooper ambush when you take the gear, portal storms every few in-game hours and a HECU supply drop each day.
• Black Ops: soldiers with night-vision goggles and MP5s, and female assassins with pistols, fire 3-round bursts like in Opposing Force. They're enemies of everyone: you, Race X and the HECU.
• HECU Marines: squads of Opposing Force Marines arrive to fight Race X and the Black Ops alongside you.
• Co-op for 2-4 players (experimental): press N to invite Steam friends (or they pick Join Game on you in Steam). The host's world runs the invasion and each friend appears as an HECU Marine. Connections go through Steam: no port forwarding. Hosting is tested; joining between two real Steam accounts is not yet.

You need Skyrim Special Edition (1.6.1170 to 1.7.104) and Half-Life with Opposing Force on Steam. Melty installs the rest.

Known limits: guns are held the way Skyrim holds a crossbow at rest (shots go to your crosshair). Black Ops and Race X attack anyone nearby, villagers included. The Helgen intro still plays (skip it with the console: coc Riverwood from the main menu). With Windows Smart App Control on, Windows may block the mod's files (they aren't code-signed yet).

Settings: OpForSkyrim.ini next to SkyrimSE.exe. Not affiliated with Valve, Gearbox or Bethesda.