The monster plugin made by HPB Botman allows you to add mobs in Multiplayer.
You can't directly spawn the monsters, the plugin needs cfg file with the coordinates and the name of the monster to spawn.


1-You need to make a config file, with the same of the map.
For example, there is a config file for crossfire named "crossfire_monster.cfg".

You need to make the same for every map you want to spawn.
Ex: bounce_monster.cfg, stalkyard_monster.cfg
Be sure the file is in cfg format.


2- Decide where to spawn them and get the position.

-Choose a location to spawn a spesific monster you desire.
-Type "status" to the console (be sure you are alone of the server or else it will be harder to get the exact origin).

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-Once you typed "status" to console and send it, it will send some information about you and the server.
We need these x-y-z numbers:

Example:
map     :  crossfire at: -983 x, 1304 y, -1631 z

Now, we have the x y and z coordinates, we just need the name of the monster.
When downloading this modpack, there is a file named "monster_precache.cfg".
Simply open it with any text editor, and remove the "//" from the begging of the monster names that you want to spawn.
This will simply keep precaching the monsters that you wish to keep spawning dynamicaly.


Those are also the names of the mosnters you can spawn (gargantua does work btw)

Now lets combine everything, go to your monster.cfg file, and start typing.

start with a {, then origin, delay and monster name, then close it with a }

{
origin/-983 1304 -1631
delay/10
monster/scientist
}

YOu can also define their angles (where they will look, if you don't they will spawn with a random angle)

Delay: How often this entity will respawn ?
Monster: Monster name, like barney, scientist, hgrunt etc.
Origin: Required coordinates, (x,y,z)

Now put that cfg file into your map folder.
Ex: Half-Life/valve/maps(This is where cfg file should locate)