---- Minecraft Crash Report ----
// This is a token for 1 free hug. Redeem at your nearest Mojangsta: [HUG]

Time: 17/08/20 16:22
Description: Exception initializing level

org.spongepowered.asm.mixin.transformer.throwables.MixinTransformerError: An unexpected critical error was encountered
at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:364)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClass(MixinTransformer.java:191)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClassBytes(MixinTransformer.java:178)
at org.spongepowered.asm.mixin.transformer.FabricMixinTransformerProxy.transformClassBytes(FabricMixinTransformerProxy.java:23)
at net.fabricmc.loader.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:157)
at net.fabricmc.loader.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:143)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at net.minecraft.class_3815.(class_3815.java:52)
at net.minecraft.class_3813.method_27221(class_3813.java:20)
at net.minecraft.class_3813.method_16753(class_3813.java:28)
at net.minecraft.class_3211$class_3212.method_28667(class_3211.java:32)
at net.minecraft.class_3211$class_3212.method_16655(class_3211.java:23)
at net.minecraft.class_3195.method_28657(class_3195.java:249)
at net.minecraft.class_5312.method_28622(class_5312.java:27)
at net.minecraft.class_2794.method_28508(class_2794.java:268)
at net.minecraft.class_2794.method_16129(class_2794.java:259)
at net.minecraft.class_2806.method_16556(class_2806.java:51)
at net.minecraft.class_2806$$Lambda$1729/1275603581.doWork(Unknown Source)
at net.minecraft.class_2806.method_12154(class_2806.java:219)
at net.minecraft.class_3898.method_17225(class_3898.java:568)
at net.minecraft.class_3898$$Lambda$6283/188924414.apply(Unknown Source)
at com.mojang.datafixers.util.Either$Left.map(Either.java:38)
at net.minecraft.class_3898.method_17224(class_3898.java:562)
at net.minecraft.class_3898$$Lambda$6268/1596152229.apply(Unknown Source)
at java.util.concurrent.CompletableFuture.uniCompose(CompletableFuture.java:952)
at java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:926)
at java.util.concurrent.CompletableFuture$Completion.run(CompletableFuture.java:442)
at net.minecraft.class_3900.method_17634(class_3900.java:58)
at net.minecraft.class_3900$$Lambda$6281/1966947494.run(Unknown Source)
at net.minecraft.class_3846.method_16907(class_3846.java:94)
at net.minecraft.class_3846.method_16900(class_3846.java:137)
at net.minecraft.class_3846.run(class_3846.java:105)
at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1402)
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1689)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)
Caused by: org.spongepowered.asm.mixin.throwables.MixinApplyError: Mixin [structhelp.mixins.json:StructurePoolBasedGeneratorOuterMixin] from phase [DEFAULT] in config [structhelp.mixins.json] FAILED during APPLY
at org.spongepowered.asm.mixin.transformer.MixinProcessor.handleMixinError(MixinProcessor.java:643)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.handleMixinApplyError(MixinProcessor.java:595)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:356)
... 36 more
Caused by: org.spongepowered.asm.mixin.transformer.throwables.InvalidMixinException: Unexpecteded ClassMetadataNotFoundException whilst transforming the mixin class: [MAIN Applicator Phase -> structhelp.mixins.json:StructurePoolBasedGeneratorOuterMixin -> Apply Methods -> (Lnet/minecraft/class_5455;Lnet/minecraft/class_3812;Lnet/minecraft/class_3778$class_3779;Lnet/minecraft/class_2794;Lnet/minecraft/class_3485;Lnet/minecraft/class_2338;Ljava/util/List;Ljava/util/Random;ZZLorg/spongepowered/asm/mixin/injection/callback/CallbackInfo;)V:handler$bka000$extractRoomMinMax -> Transform LVT -> var=registryManager -> desc=Lnet/minecraft/class_5455;]
at org.spongepowered.asm.mixin.transformer.MixinTargetContext.transformMethod(MixinTargetContext.java:490)
at org.spongepowered.asm.mixin.transformer.MixinApplicatorStandard.applyNormalMethod(MixinApplicatorStandard.java:523)
at org.spongepowered.asm.mixin.transformer.MixinApplicatorStandard.applyMethods(MixinApplicatorStandard.java:509)
at org.spongepowered.asm.mixin.transformer.MixinApplicatorStandard.applyMixin(MixinApplicatorStandard.java:381)
at org.spongepowered.asm.mixin.transformer.MixinApplicatorStandard.apply(MixinApplicatorStandard.java:320)
at org.spongepowered.asm.mixin.transformer.TargetClassContext.applyMixins(TargetClassContext.java:345)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:570)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:351)
... 36 more
Caused by: org.spongepowered.asm.mixin.throwables.ClassMetadataNotFoundException: net.minecraft.class_5455
at org.spongepowered.asm.mixin.transformer.MixinTargetContext.transformSingleDescriptor(MixinTargetContext.java:949)
at org.spongepowered.asm.mixin.transformer.MixinTargetContext.transformSingleDescriptor(MixinTargetContext.java:909)
at org.spongepowered.asm.mixin.transformer.MixinTargetContext.transformLVT(MixinTargetContext.java:543)
at org.spongepowered.asm.mixin.transformer.MixinTargetContext.transformMethod(MixinTargetContext.java:449)
... 43 more

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

-- Head --
Thread: Server thread
Stacktrace:
at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:364)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClass(MixinTransformer.java:191)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClassBytes(MixinTransformer.java:178)
at org.spongepowered.asm.mixin.transformer.FabricMixinTransformerProxy.transformClassBytes(FabricMixinTransformerProxy.java:23)
at net.fabricmc.loader.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:157)
at net.fabricmc.loader.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:143)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at net.minecraft.class_3815.(class_3815.java:52)
at net.minecraft.class_3813.method_27221(class_3813.java:20)
at net.minecraft.class_3813.method_16753(class_3813.java:28)
at net.minecraft.class_3211$class_3212.method_28667(class_3211.java:32)
at net.minecraft.class_3211$class_3212.method_16655(class_3211.java:23)
at net.minecraft.class_3195.method_28657(class_3195.java:249)
at net.minecraft.class_5312.method_28622(class_5312.java:27)
at net.minecraft.class_2794.method_28508(class_2794.java:268)
at net.minecraft.class_2794.method_16129(class_2794.java:259)
at net.minecraft.class_2806.method_16556(class_2806.java:51)
at net.minecraft.class_2806$$Lambda$1729/1275603581.doWork(Unknown Source)
at net.minecraft.class_2806.method_12154(class_2806.java:219)
at net.minecraft.class_3898.method_17225(class_3898.java:568)
at net.minecraft.class_3898$$Lambda$6283/188924414.apply(Unknown Source)
at com.mojang.datafixers.util.Either$Left.map(Either.java:38)
at net.minecraft.class_3898.method_17224(class_3898.java:562)
at net.minecraft.class_3898$$Lambda$6268/1596152229.apply(Unknown Source)
at java.util.concurrent.CompletableFuture.uniCompose(CompletableFuture.java:952)
at java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:926)
at java.util.concurrent.CompletableFuture$Completion.run(CompletableFuture.java:442)
at net.minecraft.class_3900.method_17634(class_3900.java:58)
at net.minecraft.class_3900$$Lambda$6281/1966947494.run(Unknown Source)
at net.minecraft.class_3846.method_16907(class_3846.java:94)

-- Affected level --
Details:
All players: 0 total; []
Chunk stats: ServerChunkCache: 529
Level dimension: minecraft:overworld
Level spawn location: World: (152,3,40), Chunk: (at 8,0,8 in 9,2; contains blocks 144,0,32 to 159,255,47), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 0 game time, 0 day time
Level name: New World
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
Known server brands: fabric
Level was modded: true
Level storage version: 0x04ABD - Anvil
Stacktrace:
at net.minecraft.server.MinecraftServer.method_3786(MinecraftServer.java:386)
at net.minecraft.server.MinecraftServer.method_3735(MinecraftServer.java:334)
at net.minecraft.class_1132.method_3823(class_1132.java:69)
at net.minecraft.server.MinecraftServer.method_29741(MinecraftServer.java:647)
at net.minecraft.server.MinecraftServer.method_29739(MinecraftServer.java:256)
at net.minecraft.server.MinecraftServer$$Lambda$6175/1606720796.run(Unknown Source)
at java.lang.Thread.run(Thread.java:745)

-- System Details --
Details:
Minecraft Version: 1.16.1
Minecraft Version ID: 1.16.1
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_51, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 59309328 bytes (56 MB) / 2147483648 bytes (2048 MB) up to 2147483648 bytes (2048 MB)
CPUs: 2
JVM Flags: 9 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xss1M -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
Fabric Mods:
adorn: Adorn 1.10.1+1.16.1
appleskin: AppleSkin 1.0.11
artifice: Artifice 0.8.1+1.16.1
artofalchemy: Art of Alchemy 1.0.0-rc2+1.16.1
astromine: Astromine 1.5.2
autoconfig1u: Auto Config v1 Updated 3.2.0-unstable
betternether: Better Nether 3.5.4
betterthanmending: BetterThanMending 1.2.0
blue_endless_jankson: jankson +
bunch-o-trinkets: Bunch O' Trinkets 1.0.1
byg: BYG 1.0.13
campanion: Campanion 1.1.13+build.35
cardinal-components-base: Cardinal Components API (base) 2.4.2
cardinal-components-block: Cardinal Components API (blocks) 2.4.2
cardinal-components-chunk: Cardinal Components API (chunks) 2.4.2
cardinal-components-entity: Cardinal Components API (entities) 2.4.2
cardinal-components-item: Cardinal Components API (items) 2.4.2
cardinal-components-level: Cardinal Components API (world saves) 2.4.2
cardinal-components-util: Cardinal Components API (utilities) 2.4.2
cardinal-components-world: Cardinal Components API (worlds) 2.4.2
chainmail: Chainmail 0.3.0
cinderscapes: Cinderscapes 1.0.7+build.43-1.16.1
cloth-basic-math: Cloth Basic Math 0.5.1
cloth-client-events-v0: Cloth Client Events v0 1.0.4
cloth-config2: Cloth Config v4 4.6.0
cloth-durability-bar-api-v1: Cloth Durability Bar API v1 1.0.7
com_moandjiezana_toml_toml4j: toml4j 0.7.2
cotton: Cotton 1.0.5
cotton-cauldron: Cotton Cauldron 1.0.4
cotton-commons: Cotton Commons 1.0.4
cotton-config: Cotton Config 1.0.0-rc.7
cotton-datapack: Cotton Datapack 1.0.5
cotton-logging: Cotton Logging 1.0.0-rc.4
cotton-player-events: Cotton Player Events 1.0.2
creativebuttonmover: Creative Button Mover 0.2.5
dark-loading-screen: Dark Loading Screen 1.4.2
dynamicfps: Dynamic FPS 1.1.4
dynamicsoundfilters: Dynamic Sound Filters 1.1.2+1.16.1
enderitemod: Enderite Mod 1.1.3
endreborn: End: Rebellion 1.7
expandedstorage: ExpandedStorage 5.3.16
experimentaway: ExperimentAway 1.0.0
extraalchemy: Extra Alchemy 1.2.1
extrapieces: Extra Pieces 2.9.0
fabric: Fabric API 0.17.0+build.386-1.16.1
fabric-api-base: Fabric API Base 0.1.3+12a8474c7c
fabric-biomes-v1: Fabric Biomes (v1) 0.2.7+059ea86602
fabric-blockrenderlayer-v1: Fabric BlockRenderLayer Registration (v1) 1.1.4+c6a8ea8902
fabric-command-api-v1: Fabric Command API (v1) 1.0.8+5ce5339802
fabric-commands-v0: Fabric Commands (v0) 0.2.0+52d3083602
fabric-containers-v0: Fabric Containers (v0) 0.1.8+045df74f02
fabric-content-registries-v0: Fabric Content Registries (v0) 0.1.9+059ea86602
fabric-crash-report-info-v1: Fabric Crash Report Info (v1) 0.1.2+b7f9825d02
fabric-diagonal-panes: Fabric Diagonal Panes 0.3.0
fabric-dimensions-v1: fabric-dimensions-v1 1.0.0+a71b305302
fabric-events-interaction-v0: Fabric Events Interaction (v0) 0.3.3+7066030f02
fabric-events-lifecycle-v0: Fabric Events Lifecycle (v0) 0.2.0+16acbe5b02
fabric-furnaces: Fabric Furnaces 1.3.1-1.16.1
fabric-game-rule-api-v1: Fabric Game Rule API (v1) 1.0.0+fe81e12502
fabric-item-api-v1: Fabric Item API (v1) 1.0.0+16acbe5b02
fabric-item-groups-v0: Fabric Item Groups (v0) 0.2.0+438f963602
fabric-key-binding-api-v1: Fabric Key Binding API (v1) 1.0.1+f404f3be02
fabric-keybindings-v0: Fabric Key Bindings (v0) 0.2.0+3fa9f7c502
fabric-language-kotlin: Fabric Language Kotlin 1.3.71+build.1
fabric-lifecycle-events-v1: Fabric Lifecycle Events (v1) 1.2.0+e83e061c02
fabric-loot-tables-v1: Fabric Loot Tables (v1) 1.0.0+386eb69e02
fabric-mining-levels-v0: Fabric Mining Levels (v0) 0.1.2+b764ce9902
fabric-models-v0: Fabric Models (v0) 0.1.0+dfdb52d602
fabric-networking-blockentity-v0: Fabric Networking Block Entity (v0) 0.2.5+b50ffc7b02
fabric-networking-v0: Fabric Networking (v0) 0.1.10+e00ecb5f02
fabric-object-builder-api-v1: Fabric Object Builder API (v1) 1.5.7+2242e77202
fabric-object-builders-v0: Fabric Object Builders (v0) 0.6.1+a2d21ddd02
fabric-particles-v1: fabric-particles-v1 0.2.1+0a6f2a7002
fabric-registry-sync-v0: Fabric Registry Sync (v0) 0.3.8+7dba2d6c02
fabric-renderer-api-v1: Fabric Renderer API (v1) 0.2.13+eae12eb802
fabric-renderer-indigo: Fabric Renderer - Indigo 0.3.4+34d6c87102
fabric-renderer-registries-v1: Fabric Renderer Registries (v1) 2.1.0+be551d3c02
fabric-rendering-data-attachment-v1: Fabric Rendering Data Attachment (v1) 0.1.3+b7f9825d02
fabric-rendering-fluids-v1: Fabric Rendering Fluids (v1) 0.1.8+b7084faa02
fabric-rendering-v0: Fabric Rendering (v0) 1.1.0+5341049002
fabric-rendering-v1: Fabric Rendering (v1) 1.1.2+346247d702
fabric-resource-loader-v0: Fabric Resource Loader (v0) 0.2.6+f41e209802
fabric-screen-handler-api-v1: Fabric Screen Handler API (v1) 1.1.0+97324d1102
fabric-tag-extensions-v0: Fabric Tag Extensions (v0) 0.2.7+a4c57d8e02
fabric-textures-v0: Fabric Textures (v0) 1.0.4+eae12eb802
fabric-tool-attribute-api-v1: Fabric Tool Attribute API (v1) 1.2.1+91fca5cd02
fabricloader: Fabric Loader 0.9.1+build.205
fermion: Fermion 2.1.191
fermion-modkeys: Fermion Modifier Keys 1.8.180-snapshot
fiber: fiber 0.23.0-1
glassdoor: Glass Doors 1.4.4-1.16
iamverysmart: I Am Very Smart 2.1.0+mc1.16.1
illuminations: Illuminations 1.0.5
indrev: Industrial Revolution 1.4.9-BETA
inventorysorter: Inventory Sorter 1.7.1-1.16
itemscroller: Item Scroller 0.15.0-dev.20200630.022843
jankson: Jankson 3.0.0+j1.2.0
kyrptconfig: Kytpt Config 1.0.4-1.16
lambdynlights: LambDynamicLights 1.2.2+1.16.1
libblockattributes_core: LibBlockAttributes (Core) 0.7.1-pre.4
libblockattributes_fluids: LibBlockAttributes (Fluids) 0.7.1-pre.4
libblockattributes_items: LibBlockAttributes (Items) 0.7.1-pre.4
libcd: LibCapableData 2.5.0+1.16.1
libgui: LibGui 2.2.0+1.16.1
libstructure: Libstructure 1.3
linkedstorage: Linked Storage 1.3.6-1.16
lithium: Lithium 0.5.1
magna: Magna 1.3.2-1.16.1
malilib: MaLiLib 0.10.0-dev.21+arne.1
mambience: MAmbience 2.1.0-1.16
minecraft: Minecraft 1.16.1
modmenu: Mod Menu 1.14.5+build.30
moenchantments: Mo'Enchantments 1.12.4-beta2
more_gems: More Gems 1.0.48
mostructures: Mo' Structures 1.0.0-pre2+mc.1.16
netheritehorsearmor: Netherite Horse Armor 0.4.2-1.16.1
ninjaphenix-container-lib: NinjaPhenix's Container Library 1.1.5
okzoomer: Ok Zoomer 4.0.0-alpha.5+1.16.1
org_jetbrains_annotations: annotations 17.0.0
org_jetbrains_kotlin_kotlin-reflect: kotlin-reflect 1.3.71
org_jetbrains_kotlin_kotlin-stdlib: kotlin-stdlib 1.3.71
org_jetbrains_kotlin_kotlin-stdlib-jdk7: kotlin-stdlib-jdk7 1.3.71
org_jetbrains_kotlin_kotlin-stdlib-jdk8: kotlin-stdlib-jdk8 1.3.71
org_jetbrains_kotlinx_kotlinx-coroutines-core: kotlinx-coroutines-core 1.3.5
org_jetbrains_kotlinx_kotlinx-coroutines-jdk8: kotlinx-coroutines-jdk8 1.3.5
parchment: Parchment 1.0.2+1.15.2
patchouli: Patchouli 1.16-39-FABRIC
phosphor: Phosphor 0.6.0+build.7
playerabilitylib: Pal 1.2.0
rare-ice: Rare Ice 0.2.1
reach-entity-attributes: Reach Entity Attribute 1.0.1
reborncore: Reborn Core 4.3.4+build.64
ringsofascension: Rings of Ascension 1.0.7
roughlyenoughitems: Roughly Enough Items 4.12.0
shapes: Shapes 2.0.0+build.10
sodium: Sodium 0.1.0
spinnery: Spinnery 3.1.14
spruceui: SpruceUI 1.5.8
static-content: Static Content 1.0.0-1.16.1
staticdata: Static Data 1.1.2
step-height-entity-attribute: Step Height Entity Attribute 1.0.0
structure-helpers: Structure Helpers 3.0.0
team_reborn_energy: Energy 0.1.0
techreborn: Tech Reborn 3.4.5+build.88
terraform: Terraform 2.1.7+build.31
thallium: Thallium 1.6
torohealth: ToroHealth Damage Indicators 1.16.1-fabric-1
trade: Trade 1.1.0
trapexpansion: Trap Expansion 1.3.2
trinkets: Trinkets 2.6.4
vanilla-hammers: Vanilla Hammers 2.0.4-1.16.1
vanillaexcavators: Vanilla Excavators 1.1.0
waila: Hwyla 1.9.22
winged: Winged Mod 1.16-1.2
wolveswitharmor: Wolves With Armor 1.5.1-1.16.1
wrenchable: Wrenchable 1.0.0+1.16.1
xaerominimap: Xaero's Minimap 20.20.0
xaeroworldmap: Xaero's World Map 1.10.0
Patchouli open book context: n/a
Player Count: 0 / 8; []
Data Packs: vanilla (incompatible), fabric/indrev, fabric/betternether, fabric/lambdynlights, fabric/astromine, fabric/iamverysmart, fabric/bunch-o-trinkets, fabric/techreborn, fabric/fabric-tool-attribute-api-v1, fabric/enderitemod, fabric/rare-ice, fabric/structure-helpers, fabric/mostructures, fabric/endreborn, fabric/expandedstorage, fabric/trapexpansion, fabric/adorn, fabric/extraalchemy, fabric/linkedstorage, fabric/libcd, fabric/vanilla-hammers, fabric/vanillaexcavators, fabric/netheritehorsearmor, fabric/campanion, fabric/wolveswitharmor, fabric/glassdoor, fabric/artofalchemy, fabric/more_gems, fabric/cotton-commons, fabric/winged, fabric/fabric-furnaces, fabric/byg, fabric/cinderscapes, extrapieces:ep_data, linkedstorage:enderstorage
Type: Integrated Server (map_client.txt)
Is Modded: Definitely; Client brand changed to 'fabric'

StructureHelper is probably a library of a mod. Your main solution is probably to remove mods one by one until you found the one causing it, after that, go to the mod dev and ask him/her.

The offender is End Rebellion / End Reborn. The 1.7 version on CurseForge is actually for 1.16.2 (at least, it pulls Structure Helpers 3.0.0).

Closing since this is not an issue with Fabric API. If you need further assistance, please join the Fabric discord https://discord.gg/v6v4pMv