Making a little buddy [Answered]

[Spaceshiporion]

I'm only a casual map creator, but this is a question I've wondered about for a while.

I wondered if it's possible to make a script that spawns an NPC next to the player that can't be hurt by the player,
and shoots enemies for you. Ideally, he sticks around in the space around the player.

I don't know how to make my own creatures yet, but for now I'd just like a marine with a rocket launcher.

Is this possible in any version of Doom Builder?

[CPLJigsoreQuandary]

You can make a custom monster and give it the +FRIENDLY flag. If you search for a mod called bfriends.pk3 (brutal friends) you can see how this works. You can make them follow the player and shoot at enemies and you can even make them stand still to guard a spot.

An easy way to make a custom monster (or friend) is to get the decorate code from the zdoom wiki and modify it.

This is the wiki page for the ZombieMan:
https://zdoom.org/wiki/Classes:ZombieMan

Assuming you know how to use Slade, you can paste this into a text file, #include it in a decorate file called DECORATE and it should run. If you want to replace the Zombieman (or any other monster) with your custom monster, type "Actor MyZombie : Zombieman replaces Zombieman" which means you are creating a new actor called MyZombie, you are taking the properties from the original Zombieman actor, and you are replacing the Zombieman with MyZombie. This will make your monster spawn anywhere a zombieman spawns.

To make this a friendly monster you can type +FRIENDLY in the section for properties (the section where player.stuff goes).

[Spaceshiporion]

You can make a custom monster and give it the +FRIENDLY flag. If you search for a mod called bfriends.pk3 (brutal friends) you can see how this works. You can make them follow the player and shoot at enemies and you can even make them stand still to guard a spot.

An easy way to make a custom monster (or friend) is to get the decorate code from the zdoom wiki and modify it.

This is the wiki page for the ZombieMan:
https://zdoom.org/wiki/Classes:ZombieMan

Assuming you know how to use Slade, you can paste this into a text file, #include it in a decorate file called DECORATE and it should run. If you want to replace the Zombieman (or any other monster) with your custom monster, type "Actor MyZombie : Zombieman replaces Zombieman" which means you are creating a new actor called MyZombie, you are taking the properties from the original Zombieman actor, and you are replacing the Zombieman with MyZombie. This will make your monster spawn anywhere a zombieman spawns.

To make this a friendly monster you can type +FRIENDLY in the section for properties (the section where player.stuff goes).

Ah, nice! Just saw this response!
Thanks for answering.

[Proydoha]

I wondered if it's possible to make a script that spawns an NPC next to the player that can't be hurt by the player,
and shoots enemies for you. Ideally, he sticks around in the space around the player.

Is this possible in any version of Doom Builder?

There is a thread Looking for a companion mod? here on forums.
One of the entries there is a template for making friendly companion monsters: Doomguy Companion [Companion Mod template]
It follows you around. I don't remember if it can be hurt by player or not but if it can - it can be fixed.

You can poke around inside of it and try to make it your own.

You'll need SLADE to peek into archives and edit files inside of them. Or if you're fine with other developer tools you can (usually) unpack any .pk3 as a regular .zip archive and work with mod files directly in any text editor that you prefer (there is a VSCode extension for example). GZDoom can load folders just fine, you don't have to repack them back into .pk3 while you're working on it.