Katzenfleisch never got around to updating the description to mention absolutely everything present in his mod or writing an official guide to teach players how to milk its features for all they're worth, so I did my best to write one myself. Here's a helpful post to inform new players of Defense what else you didn't know you can play with. Please keep in mind that the information below may still be subject to change based on if katz decides to come back and update Defense (fingers crossed, as in my opinion this gamemode is the most fun you can have in Natural Selection 2 given the dying playerbase).


NS2_def_troopers_v1 is depreciated. While it may look more visually complete, it is NOT the correct map. Do not play on it. Alien pathing is janky and only partly functional, and attempting to enter a Command Station locks your view into cursor-mode indefinitely and does not actually grant access to Commander features!

On the ns2_def_troopers map (which is the correct one), Marines receive weapons and armor upgrades from a pre-built Arms Lab automatically without the need for a Commander, based on wave progression. (Only applies to default wave, may not currently function on special waves!) On any other map, all upgrades must be purchased by a Commander like normal.
You can repair doors with your welder to keep them alive longer, but once they've been blown open, they're gone for good.

There are no hives on ns2_def_troopers, and aliens spawn from custom spawn locations in the map, therefore the only way to win on the map is to outlast the horde!


Turrets have had their health buffed, and share the same damage bonuses a player receives.

Turrets only need to be built around a battery by a Commander, but do not actually require said battery in order to operate and open fire, meaning once they have been built within the radius of a battery, that battery can even be recycled and those turrets will still work, able to open fire from anywhere without needing any battery nearby.

Batteries have drastically increased radius (really only used for building convenience, since they are not needed to keep turrets functioning), and can support up to 6 turrets per-battery. However, this turret limit only applies to the Commander placing unbuilt turrets down.

You can pick up and reposition turrets manually as a lone marine by pressing E while looking at any turret, which moves it into your 4th slot, allowing you to switch back to your weapons freely as you carry it around. To place a turret back down, hold your 4th slot turret item (looks like another welder) and left-click on floors, walls, or ceilings (just make sure they're facing the right way!)
Manually positioning turrets as a marine has huge hidden benefits. You can place them on surfaces that a Commander is not able to, and moving turrets manually as a marine can also bypass the max-turret restriction for any area/battery radius, meaning you can have a row of 30 turrets in the same room so long as you picked them up from another room and brought them over manually one by one. This makes it beneficial for the Commander to make the turret battery not in the main room where the primary choke point is, but in a safe nearby room instead, drop down your 6 turrets as a Commander, build them to completion with a MAC or as a Marine, then move each turret manually back to your main choke point and place them down wherever you please.
Doing this will remove turrets from the nearby room where the battery is located, and allow the Commander to then make 6 more turrets around that same battery! You can rinse-and-repeat this process until you have maxed out your supply limit and cannot build any more turrets. This is currently the meta strategy for fortifying a chokepoint, with gatling exos and mines as supplementary damage to defend your turret line.
(Note: batteries do not need to be fully constructed before turrets can be placed around them, they can be kept as unbuilt ghost batteries to save time.)

• Skulk Hell is a single 250+ skulks wave
  
  
• Skulk Hell (extra hard) is a single 250+ skulks wave with buffed skulk count and spawns that are not dependent on a hive, causing skulks to appear much sooner and in much larger numbers by the time they reach the Marines' front line. (This wave is currently considered the most difficult hell wave to beat while still just barely being beatable with proper planning, multiple fallback lines, plentiful doors and turrets, and lots of competent marine players using exos and grenade launchers.)
  
  
• Lerk Hell is a single 250+ lerks wave
  
  
• Mixed Hell is a single wave consisting of all alien types in aggressively plentiful quantities and is the hardest wave you can fight that still has an actual end to it. (This wave is currently considered impossible to beat until Katz makes balancing changes to the Defense gamemode.)
  
  
• Survival Hell is a single endless wave that ramps up in difficulty until it peaks in intensity and will virtually guarantee all but the strongest defense setups being overwhelmed. (This wave is currently considered impossible to beat until Katz makes balancing changes to the Defense gamemode.)
  Ramp-up frequency for Survival Hell is based on the round timer, NOT the wave start timer, meaning if you change to Survival Hell 30 minutes into an active round, the Survival Hell wave will begin at max intensity with no build-up. If you change to Survival Hell at the beginning of the round, the wave starts out with just skulks, then other alien types are slowly added to the horde every 2-5 minutes until you are fighting large quantities of all alien types all at once. A small portion of each alien type in this special endless wave will have boosted health and damage to a varying degree based on the threat-level of that alien type. For instance, the fraction of Onos' that receive this health and damage buff have the smallest buff of all other aliens, as they are the highest threat-level alien type in the horde.
  
  There are small grace periods when the Survival Hell wave loops its cycle and begins another horde of aliens. Players can use this grace period of around 1-3 minutes to move their defenses around/forward, or repair and renew their defense line before the horde resumes. (Survival Hell, on top of being poorly balanced and genuinely impossible to beat, no longer has grace periods at all. As of the date this post was updated, Survival Hell is just endless chaos and guaranteed death following shortly after for even the strongest of defenses.)
  **********
  PLEASE NOTE!: Survival Hell can sometimes break alien spawning if it is switched to at the very end of a round that has gone on for 30+ minutes. Katz has attempted to fix this, but it can still happen if a Survival Hell wave is started too late into a round or goes on for too long (which would never happen as it is currently entirely impossible to survive longer than a few minutes). If this glitch occurs, you must start a new map in order to fix it, as changing to any other waves or winning and starting a new round will result in an instant Marine win upon that new wave/round starting. As a sad result of the current faulty functionality and broken balancing of the Survival Hell wave, you should just do Lerk/Skulk Hell or maybe Skulk Hell Extra Hard instead as a grand finale to put the strength of your maxed-out front line defenses to the ultimate test.
  **********

ToW (Tug-of-War) maps from the workshop are strongly recommended to play with the Defense gamemode, as their modified layouts compliment the gamemode excellently. Unlike ns2_def_troopers, there are actually hives in ToW maps, meaning you have an alternative win condition of destroying all alien hives instead of simply surviving to the end of the last wave, allowing you to cut the game short with an early victory if you're fast/strong enough.

Here's a couple in particular you should try:

• ns2_Stag is a beautiful map that takes place inside a starship orbiting a ring world, and Home (the creator of Stag) has been gracious enough to create a modified tug-of-war version of his map such that it can be used specifically for the Defense gamemode! Stag is wonderful for Defense especially if Marines are at one end of the map and Aliens are at the other, meaning the aliens must travel all the way through the ship before reaching you, giving you ample time to prepare and slowly push up room by room with plentiful and well-balanced choke points that you can defend as you slowly take back the entire ship from the alien scourge.
  https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2622979442&searchtext=tow_stag
  (Please note: ns2_tow_stag never had its bot pathing completely perfected to the ToW layout changes (like many ToW maps), and if you build in 'Stern' or loiter there as Marines, aliens are likely to get stuck in small numbers (especially skulks) at this particular part of the map while trying to reach you, but it shouldn't happen often enough to ruin any games. If this happens to you, the only real fix is to relocate your base further up in the ship and thus cause all future-spawning aliens to path to you differently.)
  
  
• ns2_tow_summit is, in my opinion, the best map to play Defense on due to its fantastic chokepoints, easily readable minimap, and generally pleasant atmosphere/aesthetic. However, it is a map by Skejay that was made before the real ns2_summit saw its vanilla NS2 face-lift and small layout improvements.
  Cerveza Dinero, (formerly known as BerserkCore) took it upon himself to upgrade ns2_tow_summit with slightly modified nav meshes to hopefully mitigate alien stuck instances at least somewhat, and has also modified the more recent version of ns2_summit to be the tug-of-war layout as well.
  https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2622326689&searchtext=tow_summit
  ns2_tow_summit by Cerveza Dinero is a tow_summit with invisible changes to try and improve alien navigation in the map, and ns2_tow_summit_2021 is the tug-of-war layout made from the most recent version of Summit, so essentially it's just prettier but has reportedly perfectly functioning navigation meshes to prevent most, if not all alien stuck instances. The reason both are provided is because Flight Control of ns2_tow_summit is the most fun and balanced Tech Point in the map for Marines, but in tow_summit_2021 the layout is slightly changed in various places, including Flight Control, so for anyone who is picky and loved the old ns2_tow_summit Flight Control layout (like me), they can still have it on ns2_tow_summit, and those that want the prettier version and are fine with the small layout changes that drastically alter how chokepoints are fortified in Defense can play ns2_tow_summit_2021.
  (Do not use the Skejay version of ns2_tow_summit alongside Cerveza Dinero's, as the map names are the exact same and there's no telling which might take precedence if both are enabled at the same time. Cerveza Dinero's ns2_tow_summit is the one with navigation tweaks made specifically to help lessen alien stuck instances for bot pathing with the Defense gamemode, but bear in mind these still can happen on occasion, though shouldn't ruin any games when they do.)

Now, because ToW maps have actual alien hives, it is also therefore possible to win on a Survival Hell wave that has no end to horde numbers. If you strategize a forward push during the grace periods between the max-intensity horde rushes during Survival Hell and manage destroy the hive before the next horde arrives, you will win.
Be careful though, the moment a hive takes any damage, it will unleash the horde early, so it's best for your team to take position around the hive and open fire all at once to destroy it as quick as possible. Done right and with enough players, an endless Survival Hell wave can actually be defeated if all alien hives (that were previously present) are destroyed. This is generally considered the ultimate challenge for the Defense mod. (Again, sadly Survival Hell is currently impossible as of the date this post was updated, and hives also no longer auto-start the next wave upon taking damage during a grace period. Fingers crossed Katz re-implements this crucial feature to prevent easy early wins, and updates the balancing of the Defense gamemode.)

PLEASE NOTE: Alien A.I. path-finding results will vary from map to map with Tug-of-War. Aliens may occasionally get stuck in a corner of the map for a time, trying to access a part of the map that is blocked off, but their navigation meshes do not seem to tell them this. They eventually correct themselves and get unstuck, but a few may also glitch into blocked off regions of the map on rare occasions while doing this, and may even then glitch back into bounds as well, essentially teleporting through the map and past your defenses in very small numbers, usually 1-3. While still technically a glitch, it can be a fun surprise to get suddenly flanked from an undefended side by a tiny scouting party of aliens, and shouldn't be anything you or a competent team can't handle.

The servers titled

• The Thirsty Katz (when it is online)
  and
  
• The Playground

are both confirmed to host the Defense gamemode and also include the above maps.
The Playground in particular is what gets the most regular traffic for the Defense gamemode (around the time of this edit on 12/04/2022, anyway) and also has additional content mods such as Modular Exosuits 2021, new marine weapons including ones by Scatter from the NS2: Evolved workshop collection, and even several other excellent ToW maps for playing Defense on it as well.
The Playground server also has applied a few minor changes that are exclusive to the Defense gamemode to make it play better, such as:

1. A single battery can now support 128 turrets being built in one room, as opposed to the Defense gamemode's current default of only 6, which required them to be built farther back in the map and carried forward one by one by helper marines.
   
2. Turrets do 25% more damage than default Defense gamemode.
   
3. Turrets are less costly, and only consume 1 Supply Point when built, as opposed to the Defense gamemode default of 4 Supply Points.
   
4. Turrets have a longer view range, and shoot at targets further away than default Defense gamemode turret range.

The following cheat commands are your friends, use these based on what best suits your desired experience:

1. sv_cheats 1 (allows for cheat commands on your server, such as the ones listed below)
   
2. darwinmode (hp cannot drop below 1, you have infinite ammo and jetpack flight)
   
3. autobuild (all unfinished structures are fully completed, and all planted structures spawn in fully built)
   
4. alltech (unlocks access to all tech upgrades, weapons, exosuits, structures, etc, bypassing their requirements)
   
5. exosuit (places you inside a dual gattling-gun exosuit)
   
6. jetpack (puts a jetpack on your back, but will reset all your weapons to default (rifle, pistol, and hatchet))
   
7. spawn sentry (spawns a partially constructed turret at your crosshair that can then be picked up and moved manually. Good for creating more turrets than your max supply would normally allow)
   
8. spawn armory (spawns a partially constructed marine armory at your crosshair)
   
9. spawn commandstation (spawns a partially constructed command station at your crosshair)
   
10. give mac (spawns a mac helper drone on your head that will construct/repair things nearby automatically)
    
11. spawn infantryportal (spawns partially constructed Marine respawn point at your crosshair)
    
12. give hmg (puts a heavy machinegun in your hands for weapon slot 1)
    
13. give flamethrower (puts a flamethrower in your hands for weapon slot 1)
    
14. pres 100 (gives you 100 player resources to use as a Marine for purchasing equipment from an armory or prototype lab)
    
15. tres 200 (gives you 200 team resources to use as a Commander for building structures)
    
16. nw (short for "Next Wave", starts the next wave if no aliens are spawning, or if you want to skip a grace period and make the aliens of the upcoming horde push/wave begin spawning in immediately)
    
17. nobot (toggles off further alien bots from spawning in, type it again to turn alien bot spawning back on)

***Katz says his interest for NS2 has dwindled significantly overtime, and he has taken huge hiatuses from NS2 in the past and will likely take more in the future, but may still be willing to keep Defense functioning if future updates to NS2 break it or if community interest boosts his motivation in the future. If any changes/updates to the Defense gamemode occur, please remember that all the above information is only as accurate as the date this post was edited. If this post was last edited months or years ago, there's a good chance the above information is anywhere from loosely accurate to totally inaccurate, as updates to the mod (or NS2 itself) may have taken place since then! Cross-reference this post's last-edited date and the mod's last-updated date to gauge how accurate the info is!

Remember that Katzenfleisch is a busy frenchie, and if you'd like to see this gamemode receive further support or updates, please leave an encouraging comment and thumbs up on this workshop submission so he knows we all still greatly enjoy this gamemode he's built.***