[DISCLAIMER]
This guide is outdated because a bug was introduced that prevented the "death" sequence from occurring. As such, the gamemode softlocks at the end of that wave.

Here was the original guide:

Hello everybody! XenThug Horde Defense is one of my favorite custom maps/gamemodes for HL:A and I have many hours playing it. After talking with Manello, the mod creator, it would seem that people could use some pointers on lasting a while, so I have created this guide. This guide goes into detail about various secrets around the map, so I recommend playing through first as there will be SPOILERS for the warehouse map.

If you don't know what mod I'm referring to, here's the original post: https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2058494913

Just a heads up, I use the full Valve Index kit on a RTX 3070 with an i7-6800k. I cannot guarantee the same experience on varying hardware setups!

With that stated, let's jump right in, shall we?

Here's some basic information about how the mod operates:

• Each wave has a predetermined amount of enemies and are in a specific order.
  
• There are 18 waves in a set, then it goes through the waves again, but each enemy has more health.
  
• Resin drop is 0-2 per kill.

When you first load the level, it's on the floor right in front of you. Can't miss it.

In order to obtain the shotgun, you first must unlock the office (more details about the office later on in the guide). The yellow key card is sitting on the hood of one of the cars, in front of the table with the crowbar. Once you have the card, you are able to unlock the single door that leads into the office. Once in the office, look immediately left and you can see the shotgun with 6 shells sitting on the rack.

This one is easily missed, but's simple to get to. Assuming the stuff is still piled up in the corner in front of the office, just grab one of the big blue barrels and place it on the pile to be able to get onto the roof of the office.

Once on the roof, head forever a little and look to the right. Between big boxes should be a few blue crates. At the bottom of one of the crates is the SMG and a cell.

I technically count this as a weapon, because it does explicit damage to everything. It's sitting on the table behind the two cars, next to the office door.

This will be the machine you go to most often as it serves both pistol ammo and shotgun shells, but it also sells Xen grenades. It's near the central area, in front of stacks of barrels. It is easily visible from most areas of the map.

The second machine is hidden slightly, as it's in the dark area near the back of the big freight truck. It sells health syringes which will be the only way to heal once the health station runs out (more details about the health station later in the guide). The bottles and toilet paper are not purchasable.

To be able to access the third machine, you need to unlock the office (more details about the office later in the guide). This machine is against the back wall and sells the SMG cells, the blue key card to unlock the double doors, as well as grub vials. It is not recommended to buy grub vials though, because one in the health station currently can not be removed.

The last vending machine is on the roof of the office, in the very back corner. It sells the standard grenades, as well as placeable tripmines. Unfortunately, the gas canisters can not be purchased at this time.

The office will be your best friend throughout the entire time you're alive. Look at other sections on how to unlock it, as well as more information about the vending machine and shotgun inside.

Here is your only true safe space as nothing that spawns can easily get inside. It's a good place to take a break, heal up, reload, and store any items that you don't want to constantly carry around with you. For me personally, I like leaving stuff on the front table because it's easy to get to from the double doors.

The office is only as safe as you make it. Meaning, DON'T LEAVE THE DOORS OPEN!!! Stuff can wander in and out, so if you need to quickly run in to heal up before heading back out, but you left that side door open, you may be greeted a surprise you were not expecting.

However, not only the office be used to keep yourself safe on the inside, but also be keeping you on the outside. Trapping an enemy in the office is a good tactic if you need to run out and grab more supplies from the various vending machines.

During the initial startup (which is further explained later in the guide) there are several items lying around that you should collect, before things become challenging. There's no specific order to collecting most things, so just pick them up as you go along.

Before things get rough, you'll want to obtain all three guns, as well as the crowbar. Their locations as well as how to obtain them are described earlier in the guide.

In addition to the 5 resin you start out with, there is a lot that are just lying around when you load the level. Here are the locations for all of them:

• On the top of the barrel pile.
  
• On top of the wooden box pile next to the barrels.
  
• On top of the shorter box near the gnome.
  
• In the back of the freight truck.
  
• In the front of the van
  
• In the back of the van.
  
• In a cardboard box at the back wall, near the office door.
  
• On the roof of the office.

The first key card you need is on the hood of the green car next to the office (more details about the office are later in the guide), in front of the table that has the crowbar.

This will unlock the single door in the side of the office. Once inside the office, go to the vending machine in the back and purchase the blue key card. You only need to purchase it once. With the blue card, you can unlock the big double doors that lead into the office.

Upon first jumping in, there's a good methodology on how to be prepared before things start getting difficult. Make sure to read the section "Starter Items" before going through this list as it explains some objects in greater detail.

First, grab that pistol, load up, and store all the extra mags in your backpack. Next, start going for that resin that's lying around as well as the other starter items. The first wave only has 5 headcrabs to start out with. While you're still collecting everything, it's most manageable to only kill 4 of the headcrabs and if you want, you can even trap the last one in the office if you really don't want to deal with him. You'll also want to have the grub smashed and health station ready so that you don't need to wait for it to be ready at a critical time.

Alright, time to jump on in! This first set is relatively easy and gives you a preview of the different enemies you will be facing throughout. Here's my recommended strategy for killing things. This is the base that can be applied to later sets as well.

• Use the shotgun on headcrabs, poison headcrabs, zombies, and manhacks. If you're in really close range of a combine, aim for the head/canister area. You will be using the shotgun most often. It's good to stock up to at least 30 shells when you have the opportunity.
  
• The pistol is good against armored headcrabs (hitting the heart is always instakill), combine at a distance, and antlions. You'll be using the pistol semi-regularly, so it's good to have at least 5 magazines (50 bullets) stocked up.
  
• The SMG does less damage than the pistol and the cells are at a higher price, but it can still be effective against medium-long range combine as well as antlions.
  
• The crowbar isn't very effective in damage-dealing, but during Set 1, it can still be used to kill lone headcrabs of any kind. Zombies and manhacks hit it out of your hands, combine do damage way faster to you than you can do to them, and you can't safely get close enough to an antlion to hit it.
  
• Xen grenades/grenades are effective against groups of enemies of all types, but on the first set, you usually shouldn't need to use them.

• Headcrabs - One hit from the shotgun is super effective. Either quickly rush up to them, or you can hit them mid-air.
  
• Poison Headcrabs - Also one hit from the shotgun. Same tactic as the regular headcrabs.
  
• Armored Headcrabs - A single bullet to the heart is all it takes. It's best to aim and shoot in it's little "I'm going to pounce!" phase where it lifts up for a moment, before it goes back down, and then jumps at you.
  
• Zombies - A single headshot with the shotgun kills the zombie and knocks the headcrab off. Every killed zombie drops the headcrab, so be prepared to kill it as well.
  
• Combine - If you can hit the valve on their back, then it's explosion is an instakill and also slightly damages anything else nearby. Otherwise, it will take a couple of shots to kill them. Note: Combine in later waves spawn with grenades on their chest. Hitting those and setting them off will also be an instakill, but it's generally easier to hit the valve.
  
• Manhacks - These annoying buggers go down relatively quickly, and you don't need to be that close yet with the shotgun to take them out.
  
• Antlions - A single pistol shot to both limbs, then one more for it's abdomen once it lights up is very effective. Note: Taking out the limbs can also provide extra resin!

And then there's Lightning Dog... You'll only see him once each set and he spawns on wave 4. It's best to take out the other zombies and headcrabs before going after him. He has relatively a lot of health and will require a decent amount of direct shotgun blasts to take him out. Be prepared though, he is a runner! A good strategy to to quickly run up to him, like headcrabs. However, if too close then he will jump at you. But don't be too far, or else he'll spit at you. If you get hit by his electric acid, it will bug at your meters momentarily, and you wont be able to move or quick turn. On this first set, he's not that hard to take out, but his health will start getting extreme in later sets.

Made it past the first set? Good job! In general, things will feel relatively the same as Set 1, and you might not notice much of a difference, but there are a few new things to watch out for. Health has also doubled since set one.

• Headcrabs still require only one shotgun blast, but you may need to be a little bit closer to them.
  
• Poison headcrabs and zombies now require two shotgun blasts
  
• Combine now require being shot more times, but one hit to the tank is still instakill.
  
• Manhacks now require that you be noticeably closer to be able to one-shot them with the shotgun.
  
• If using the pistol against antlions, taking off the limbs and killing them is still simple.
  
• Lightning Dog is not fun to work with, but he will still go down in a relatively quick fashion.

If you made it to wave 37, then things start getting serious and you will need to be prepared. Enemy health has doubled again, so now they're at 400% as opposed to just 100% in Set 1.

• Headcrabs now require two shotgun blasts, which means no longer can you easily take them out mid-air.
  
• Poison headcrabs and zombies now require three hits from the shotgun, so watch out.
  
• Combine now take significantly longer to kill, so it's best to aim for the tank valve.
  
• Manhacks can still go down in one hit from the shotgun, but you do need to be really close to them, which is not ideal if you're getting swarmed.
  
• Antlion limbs come off easily, but it may take a couple shots to abdomen to be able to kill them.

Lightning Dog has now become your worst enemy. Make sure you have AT LEAST 40 shotgun shells to be able to take him out. Which may require spending a lot resin. However, once you lose all that resin on ammo, then ammo on Lightning Dog, things will only go from bad to worse. Be prepared for the economy collapse, because it will happen before you reach Set 4.

During this set (especially after killing Lightning Dog who has an insane amount of health) you will be buying so much ammo because of how things just don't like dying. However, the resin drop remains the same which means you won't be able to make the resin back and eventually you'll come to 0 resin and 0 ammo. So what's left to do?

If you make it to the point where you can't afford to buy ammo, then your only real option is to prop-kill zombies and headcrabs, and hope you don't get anything else. Tires and metal barrels are effective against headcrabs and zombies, and you can also use the silver gas can and blue storage crate against headcrabs. Then there's also my "Boomerang Crowbar" method, but more detail about that later in the guide.

If you've somehow made it to wave 55, then don't expect to be able to last much longer. All things now have 800% of their original health. By now, you've probably been playing for about 3 hours and your score is about 6k, but things will only become more impossible from here. And then there's your fourth encounter with Lightning Dog who already collapsed your economy last time you saw him. He's only returned once more because he knows you most likely won't be able to kill him again.

With the map in it's current state, I declare it legitimately impossible to pass Set 4 (unless you just want to spam the emergency button and lose your entire score) using the strategies I have refined over the many hours I've spent playing it.

Unless you use the button on Lightning Dog starting from the third time you see him. That might be able to delay the economy crash for a little bit longer. THIS IS UNTESTED THOUGH!!!

There are plenty of things in the map to climb on, so elevation is at your advantage against all enemy types other than the combine and manhacks.

This is relatively straightforward that is most effective against zombies. If you want to use the crowbar on headcrabs, it's easier to just whack them. All you do is throw the crowbar at the zombie (make sure to aim that the curved part is facing them) then once it hits, just pull it back to you. The damage-dealing part of the crowbar is the area around the tip of the curved part, as if you were just trying to swing the crowbar normally. However, this process is really slow and chances are, you will eventually lose the crowbar because it has bad collision. This is mostly just a last-resort thing as you can also get tired from throwing it anyways.

This is kind of an advanced move and it also uses up a lot of ammo, unless you get lucky. It works from inside the office and is most effective against the combine. With one hand, hold onto one of the doors and open it slightly, then with the pistol (I suppose the SMG as well, but it's not as effective), put out of the slightly open door, then peer through the glass at the enemy. It may take a few tries to hit the combine, but it mainly just requires good depth perception and such to be able to angle the pistol just right. The combine don't usually shoot unless they actually see your head (they can't see through the glass in the doors) and this is most effective against stationary combine. Moving ones are even harder.

Thanks for reading! If mechanics change and such, or something needs fixing, then comment down below and I'll get to it. If I come across anything else new, then I will also be sure to update the guide. If you have any personal inquiries, then you can message me on Discord at Xelanater#9381

Until next time!

Want to know my current high score? I'll be keeping this up to date: