Mod using minecraft magma

[RobinCirex]

Hey, I don't know if this is the correct place to ask, but I'm gonna try anyway. 

Someone asked me to make a mod which makes it so that specific mods of the mod Ice and Fire can't grief the environment in worldguarded regions. 

For that, I have to use a spigot plugin as a dependency in a forge mod. When I built the mod using gradlew build and started the server, it can't use the libraries and throws a ClassNotFoundException where I use the worldguard things (which makes sense). 

Does someone know how I could do this?
I added the plugins (worldguard and worldedit) to the ./libs folder too

 

[RobinCirex]

23 minutes ago, diesieben07 said:

So just to get this straight, you did do this in a server where those plugins are installed? 
Please show your build.gradle and how you added the dependencies there, too.

Yes, those plugins are installed. 

I haven't added the dependencies in the build.gradle because it says "    // you may put jars on which you depend on in ./libs"

[Novârch]

3 minutes ago, RobinCirex said:

you may put jars on which you depend on in ./libs"

You still have to specify them in the build.gradle.

[RobinCirex]

3 minutes ago, diesieben07 said:

What version of Minecraft is this? That looks like 1.12 which is not supported.

It is, as the ice and  fire mod is for 1.12. But that doesn't change anything, right?