[15Dec2021 15:21:16.156] [Render thread/FATAL] [net.minecraftforge.fml.ModLoader/CORE]: Error during pre-loading phase
net.minecraftforge.fml.ModLoadingException: Mod File ExtremeReactors2-1.18-2.0.32.jar needs language provider javafml:38 or above, and below 39 to load
§7We have found 39
at net.minecraftforge.fml.ModLoadingException.lambda$fromEarlyException$0(ModLoadingException.java:64) ~[fmlcore-1.18.1-39.0.5.jar%23327!:?]
at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197) ~[?:?]
at java.util.AbstractList$RandomAccessSpliterator.forEachRemaining(AbstractList.java:720) ~[?:?]
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509) ~[?:?]
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499) ~[?:?]
at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150) ~[?:?]
at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173) ~[?:?]
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[?:?]
at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:596) ~[?:?]
at java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:276) ~[?:?]
at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1625) ~[?:?]
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509) ~[?:?]
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499) ~[?:?]
at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921) ~[?:?]
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[?:?]
at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:682) ~[?:?]
at net.minecraftforge.fml.ModLoader.(ModLoader.java:108) ~[fmlcore-1.18.1-39.0.5.jar%23327!:?]
at net.minecraftforge.fml.ModLoader.get(ModLoader.java:140) ~[fmlcore-1.18.1-39.0.5.jar%23327!:?]
at net.minecraftforge.client.loading.ClientModLoader.lambda$begin$1(ClientModLoader.java:106) ~[forge-1.18.1-39.0.5-universal.jar%23330!:?]
at net.minecraftforge.client.loading.ClientModLoader.lambda$createRunnableWithCatch$4(ClientModLoader.java:127) ~[forge-1.18.1-39.0.5-universal.jar%23330!:?]
at net.minecraftforge.client.loading.ClientModLoader.begin(ClientModLoader.java:106) ~[forge-1.18.1-39.0.5-universal.jar%23330!:?]
at net.minecraft.client.Minecraft.(Minecraft.java:458) ~[client-1.18.1-20211210.034407-srg.jar%23326!:?]
at net.minecraft.client.main.Main.main(Main.java:169) ~[client-1.18.1-20211210.034407-srg.jar%23326!:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
at net.minecraftforge.fml.loading.targets.CommonClientLaunchHandler.lambda$launchService$0(CommonClientLaunchHandler.java:45) ~[fmlloader-1.18.1-39.0.5.jar%2323!:?]
at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:37) [modlauncher-9.0.7.jar%235!:?]
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:53) [modlauncher-9.0.7.jar%235!:?]
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:71) [modlauncher-9.0.7.jar%235!:?]
at cpw.mods.modlauncher.Launcher.run(Launcher.java:106) [modlauncher-9.0.7.jar%235!:?]
at cpw.mods.modlauncher.Launcher.main(Launcher.java:77) [modlauncher-9.0.7.jar%235!:?]
at cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:26) [modlauncher-9.0.7.jar%235!:?]
at cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:23) [modlauncher-9.0.7.jar%235!:?]
at cpw.mods.bootstraplauncher.BootstrapLauncher.main(BootstrapLauncher.java:90) [bootstraplauncher-0.1.17.jar:?]

Can confirm, running into the same issue on version 1.18.1

This is because the creator of the mod still hasnt updated to 1.18.1. It is still looking for ForgeModLoader 38. But Forge is now on version 39 with the release of 1.18.1. I've been patiently awaiting an update as well :). Just have to remove the mod until he updates it!

1.18.1 will be out today.

PS: Please check the #issue channel on my discord server before posting here

https://discord.com/channels/801004642892382248/801005146883489822/920520980592484383