[05:53:19] [main/FATAL]: Failed to start the minecraft server
java.lang.RuntimeException: Could not execute entrypoint stage 'main' due to errors, provided by 'mobfilter'!
at net.fabricmc.loader.impl.entrypoint.EntrypointUtils.lambda$invoke0$0(EntrypointUtils.java:51) ~[fabric-loader-0.13.3.jar:?]
at net.fabricmc.loader.impl.util.ExceptionUtil.gatherExceptions(ExceptionUtil.java:33) ~[fabric-loader-0.13.3.jar:?]
at net.fabricmc.loader.impl.entrypoint.EntrypointUtils.invoke0(EntrypointUtils.java:49) ~[fabric-loader-0.13.3.jar:?]
at net.fabricmc.loader.impl.entrypoint.EntrypointUtils.invoke(EntrypointUtils.java:35) ~[fabric-loader-0.13.3.jar:?]
at net.fabricmc.loader.impl.game.minecraft.Hooks.startServer(Hooks.java:62) ~[fabric-loader-0.13.3.jar:?]
at net.minecraft.server.Main.main(Main.java:106) [server-intermediary.jar:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:416) [fabric-loader-0.13.3.jar:?]
at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:77) [fabric-loader-0.13.3.jar:?]
at net.fabricmc.loader.impl.launch.knot.KnotServer.main(KnotServer.java:23) [fabric-loader-0.13.3.jar:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
at net.fabricmc.loader.impl.launch.server.FabricServerLauncher.main(FabricServerLauncher.java:66) [fabric-loader-0.13.3.jar:?]
at net.fabricmc.installer.ServerLauncher.main(ServerLauncher.java:64) [fabric-server-mc.1.18.1-loader.0.13.3-launcher.0.10.2.jar:0.10.2]
Caused by: java.lang.RuntimeException: Cannot load class net.fabricmc.fabric.api.client.event.lifecycle.v1.ClientLifecycleEvents in environment type SERVER
at net.fabricmc.loader.impl.transformer.FabricTransformer.transform(FabricTransformer.java:59) ~[fabric-loader-0.13.3.jar:?]
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPreMixinClassByteArray(KnotClassDelegate.java:282) ~[fabric-loader-0.13.3.jar:?]
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:240) ~[fabric-loader-0.13.3.jar:?]
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.tryLoadClass(KnotClassDelegate.java:150) ~[fabric-loader-0.13.3.jar:?]
at net.fabricmc.loader.impl.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:155) ~[fabric-loader-0.13.3.jar:?]
at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?]
at net.pcal.mobfilter.MFInitializer.onInitialize(MFInitializer.java:18) ~[mobfilter-0.0.1.jar:?]
at net.fabricmc.loader.impl.entrypoint.EntrypointUtils.invoke0(EntrypointUtils.java:47) ~[fabric-loader-0.13.3.jar:?]
... 16 more

I wasn't ever able to reproduce this. I assume it's a fabric API version mismatch.

If you're still seeing this, please reopen the issue. Thanks!