Hi! Maybe I'm doing something wrong, but... :

et.minecraftforge.fml.loading.EarlyLoadingException: Could not execute entrypoint stage 'main' due to errors, provided by 'death_knights' at 'elocindev.deathknights.DeathKnights'!
at org.sinytra.connector.loader.ConnectorEarlyLoader.createLoadingException(ConnectorEarlyLoader.java:81) ~[Connector-1.0.0-beta.46+1.20.1.jar%23385!/:1.0.0-beta.46+1.20.1] {}
at org.sinytra.connector.loader.ConnectorEarlyLoader.createGenericLoadingException(ConnectorEarlyLoader.java:77) ~[Connector-1.0.0-beta.46+1.20.1.jar%23385!/:1.0.0-beta.46+1.20.1] {}
at org.sinytra.connector.mod.ConnectorLoader.load(ConnectorLoader.java:55) ~[Connector-1.0.0-beta.46+1.20.1-mod.jar%23389!/:1.0.0-beta.46+1.20.1] {re:mixin,re:classloading}
at net.minecraft.client.Minecraft.handler$fha000$connectormod$earlyInit(Minecraft.java:24945) ~[client-1.20.1-20230612.114412-srg.jar%23618!/:?] {re:mixin,pl:accesstransformer:B,pl:connector_pre_launch:A,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:mixin:A,pl:connector_pre_launch:A,pl:runtimedistcleaner:A}
at net.minecraft.client.Minecraft.(Minecraft.java:424) ~[client-1.20.1-20230612.114412-srg.jar%23618!/:?] {re:mixin,pl:accesstransformer:B,pl:connector_pre_launch:A,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:mixin:A,pl:connector_pre_launch:A,pl:runtimedistcleaner:A}
at net.minecraft.client.main.Main.main(Main.java:182) ~[forge-47.3.11.jar:?] {re:mixin,pl:connector_pre_launch:A,pl:runtimedistcleaner:A,re:classloading,pl:mixin:APP:flywheel.mixins.json:ClientMainMixin from mod flywheel,pl:mixin:APP:blinkload-common.mixins.json:client.main.ClientMainMixin from mod blinkload,pl:mixin:A,pl:connector_pre_launch:A,pl:runtimedistcleaner:A}
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?] {}
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?] {}
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?] {}
at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?] {re:mixin}
at net.minecraftforge.fml.loading.targets.CommonLaunchHandler.runTarget(CommonLaunchHandler.java:111) ~[fmlloader-1.20.1-47.3.11.jar:?] {}
at net.minecraftforge.fml.loading.targets.CommonLaunchHandler.clientService(CommonLaunchHandler.java:99) ~[fmlloader-1.20.1-47.3.11.jar:?] {}
at net.minecraftforge.fml.loading.targets.CommonClientLaunchHandler.lambda$makeService$0(CommonClientLaunchHandler.java:25) ~[fmlloader-1.20.1-47.3.11.jar:?] {}
at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:30) ~[modlauncher-10.0.9.jar:?] {}
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:53) ~[modlauncher-10.0.9.jar:?] {}
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:71) ~[modlauncher-10.0.9.jar:?] {}
at cpw.mods.modlauncher.Launcher.run(Launcher.java:108) ~[modlauncher-10.0.9.jar:?] {}
at cpw.mods.modlauncher.Launcher.main(Launcher.java:78) ~[modlauncher-10.0.9.jar:?] {}
at cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:26) ~[modlauncher-10.0.9.jar:?] {}
at cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:23) ~[modlauncher-10.0.9.jar:?] {}
at cpw.mods.bootstraplauncher.BootstrapLauncher.main(BootstrapLauncher.java:141) ~[bootstraplauncher-1.1.2.jar:?] {}
Caused by: java.lang.RuntimeException: Could not execute entrypoint stage 'main' due to errors, provided by 'death_knights' at 'elocindev.deathknights.DeathKnights'!
at net.fabricmc.loader.impl.FabricLoaderImpl.lambda$invokeEntrypoints$0(FabricLoaderImpl.java:133) ~[Connector-1.0.0-beta.46+1.20.1.jar%23385!/:1.0.0-beta.46+1.20.1] {}
at net.fabricmc.loader.impl.util.ExceptionUtil.gatherExceptions(ExceptionUtil.java:33) ~[Connector-1.0.0-beta.46+1.20.1.jar%23385!/:1.0.0-beta.46+1.20.1] {}
at net.fabricmc.loader.impl.FabricLoaderImpl.invokeEntrypoints(FabricLoaderImpl.java:131) ~[Connector-1.0.0-beta.46+1.20.1.jar%23385!/:1.0.0-beta.46+1.20.1] {}
at org.sinytra.connector.mod.ConnectorLoader.load(ConnectorLoader.java:44) ~[Connector-1.0.0-beta.46+1.20.1-mod.jar%23389!/:1.0.0-beta.46+1.20.1] {re:mixin,re:classloading}
... 18 more
Caused by: java.lang.NoSuchMethodError: 'net.minecraft.resources.ResourceLocation elocindev.necronomicon.api.ResourceIdentifier.get(java.lang.String)'
at elocindev.deathknights.registry.ArmorRegistry.(ArmorRegistry.java:101) ~[Death_Knights-0.5.0beta+1.20.1_mapped_srg_1.20.1.jar%231242!/:?] {re:classloading}
at elocindev.deathknights.config.entries.ArmorConfig.(ArmorConfig.java:12) ~[Death_Knights-0.5.0beta+1.20.1_mapped_srg_1.20.1.jar%231242!/:?] {re:classloading}
at elocindev.deathknights.config.Configs$Items.(Configs.java:50) ~[Death_Knights-0.5.0beta+1.20.1_mapped_srg_1.20.1.jar%231242!/:?] {re:classloading}
at elocindev.deathknights.config.ConfigLoader.init(ConfigLoader.java:27) ~[Death_Knights-0.5.0beta+1.20.1_mapped_srg_1.20.1.jar%231242!/:?] {re:classloading}
at elocindev.deathknights.DeathKnights.onInitialize(DeathKnights.java:35) ~[Death_Knights-0.5.0beta+1.20.1_mapped_srg_1.20.1.jar%231242!/:?] {re:mixin,re:classloading}
at net.fabricmc.loader.impl.FabricLoaderImpl.invokeEntrypoints(FabricLoaderImpl.java:129) ~[Connector-1.0.0-beta.46+1.20.1.jar%23385!/:1.0.0-beta.46+1.20.1] {}
at org.sinytra.connector.mod.ConnectorLoader.load(ConnectorLoader.java:44) ~[Connector-1.0.0-beta.46+1.20.1-mod.jar%23389!/:1.0.0-beta.46+1.20.1] {re:mixin,re:classloading}
... 18 more

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Thread: Render thread
Suspected Mods: NONE
Stacktrace:
at org.sinytra.connector.loader.ConnectorEarlyLoader.createLoadingException(ConnectorEarlyLoader.java:81) ~[Connector-1.0.0-beta.46+1.20.1.jar%23385!/:1.0.0-beta.46+1.20.1] {}
at org.sinytra.connector.loader.ConnectorEarlyLoader.createGenericLoadingException(ConnectorEarlyLoader.java:77) ~[Connector-1.0.0-beta.46+1.20.1.jar%23385!/:1.0.0-beta.46+1.20.1] {}
at org.sinytra.connector.mod.ConnectorLoader.load(ConnectorLoader.java:55) ~[Connector-1.0.0-beta.46+1.20.1-mod.jar%23389!/:1.0.0-beta.46+1.20.1] {re:mixin,re:classloading}
at net.minecraft.client.Minecraft.handler$fha000$connectormod$earlyInit(Minecraft.java:24945) ~[client-1.20.1-20230612.114412-srg.jar%23618!/:?] {re:mixin,pl:accesstransformer:B,pl:connector_pre_launch:A,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:mixin:A,pl:connector_pre_launch:A,pl:runtimedistcleaner:A}
at net.minecraft.client.Minecraft.(Minecraft.java:424) ~[client-1.20.1-20230612.114412-srg.jar%23618!/:?] {re:mixin,pl:accesstransformer:B,pl:connector_pre_launch:A,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:mixin:A,pl:connector_pre_launch:A,pl:runtimedistcleaner:A}

I believe its related to the versioning not being semver-compliant (it should be 0.5.0-beta afaik)

EDIT: nvm, openin the jar and changing it to 0.5.0-beta still crashes, just without a warning about the semver

This actually does work with Synstra connector, for me. It's possible you didn't install trinkets, which is a dependency for Spell Engine, but for some reason the others don't crash without it.

This actually does work with Synstra connector, for me. It's possible you didn't install trinkets, which is a dependency for Spell Engine, but for some reason the others don't crash without it.

I have the exact same problem even with Trinckets. Could it be possible to see your mod list? (for mine everything is up to date)

Please report to the Connector developer