So, there seems to be an issue with the Seasons mod; that's yet to be fixed by WeatherPony; it's been addressed, but so far there's been no fix issued on their end.

Seems the issue is wrapped around The Betweenlands Block Registry; here is the error log:

---- Minecraft Crash Report ----
// I feel sad now :(

Time: 1/13/17 6:33 PM
Description: Initializing game

java.lang.IllegalAccessError: tried to access class thebetweenlands.blocks.BLBlockRegistry$8 from class weatherpony.partial.generated.thebetweenlands.blocks.BLBlockRegistry$8.proxyNum0
at weatherpony.partial.generated.thebetweenlands.blocks.BLBlockRegistry$8.proxyNum0.call2(Unknown Source)
at weatherpony.partial.generated.thebetweenlands.blocks.BLBlockRegistry$8.proxyNum0.call2(Unknown Source)
at weatherpony.partial.CallWrapper.call(CallWrapper.java:52)
at weatherpony.partial.HookListenerHelper.callProxy(HookListenerHelper.java:85)
at weatherpony.partial.HookListenerHelper.callNext(HookListenerHelper.java:71)
at weatherpony.seasons.pml.edits.block.BlockFlowerEdits$RegisterBlockIcons.call2(BlockFlowerEdits.java:86)
at weatherpony.seasons.pml.edits.block.BlockFlowerEdits$RegisterBlockIcons.call2(BlockFlowerEdits.java:71)
at weatherpony.partial.CallWrapper.call(CallWrapper.java:52)
at weatherpony.partial.HookListenerHelper.callNext(HookListenerHelper.java:75)
at weatherpony.seasons.pml.edits.texturefixes.TextureRetrivalDuringCreation$RegisterBlockIcons.call2(TextureRetrivalDuringCreation.java:37)
at weatherpony.seasons.pml.edits.texturefixes.TextureRetrivalDuringCreation$RegisterBlockIcons.call2(TextureRetrivalDuringCreation.java:21)
at weatherpony.partial.CallWrapper.call(CallWrapper.java:52)
at weatherpony.partial.HookListenerHelper.callNext(HookListenerHelper.java:75)
at weatherpony.partial.HookListenerHelper.distribute(HookListenerHelper.java:64)
at weatherpony.partial.HookListenerHelperPool.distribute(HookListenerHelperPool.java:134)
at weatherpony.partial.internal.GeneralHookManager.rigAndDistributeCall(GeneralHookManager.java:276)
at thebetweenlands.blocks.BLBlockRegistry$8.func_149651_a(BLBlockRegistry.java)
at net.minecraft.client.renderer.texture.TextureMap.func_110573_f(TextureMap.java:335)
at net.minecraft.client.renderer.texture.TextureMap.(TextureMap.java:62)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:540)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:878)
at net.minecraft.client.main.Main.main(SourceFile:148)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at weatherpony.pml.premain.ReplacementMainThread.run(ReplacementMainThread.java:104)

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

-- Head --
Stacktrace:
at weatherpony.partial.generated.thebetweenlands.blocks.BLBlockRegistry$8.proxyNum0.call2(Unknown Source)
at weatherpony.partial.generated.thebetweenlands.blocks.BLBlockRegistry$8.proxyNum0.call2(Unknown Source)
at weatherpony.partial.CallWrapper.call(CallWrapper.java:52)
at weatherpony.partial.HookListenerHelper.callProxy(HookListenerHelper.java:85)
at weatherpony.partial.HookListenerHelper.callNext(HookListenerHelper.java:71)
at weatherpony.seasons.pml.edits.block.BlockFlowerEdits$RegisterBlockIcons.call2(BlockFlowerEdits.java:86)
at weatherpony.seasons.pml.edits.block.BlockFlowerEdits$RegisterBlockIcons.call2(BlockFlowerEdits.java:71)
at weatherpony.partial.CallWrapper.call(CallWrapper.java:52)
at weatherpony.partial.HookListenerHelper.callNext(HookListenerHelper.java:75)
at weatherpony.seasons.pml.edits.texturefixes.TextureRetrivalDuringCreation$RegisterBlockIcons.call2(TextureRetrivalDuringCreation.java:37)
at weatherpony.seasons.pml.edits.texturefixes.TextureRetrivalDuringCreation$RegisterBlockIcons.call2(TextureRetrivalDuringCreation.java:21)
at weatherpony.partial.CallWrapper.call(CallWrapper.java:52)
at weatherpony.partial.HookListenerHelper.callNext(HookListenerHelper.java:75)
at weatherpony.partial.HookListenerHelper.distribute(HookListenerHelper.java:64)
at weatherpony.partial.HookListenerHelperPool.distribute(HookListenerHelperPool.java:134)
at weatherpony.partial.internal.GeneralHookManager.rigAndDistributeCall(GeneralHookManager.java:276)
at thebetweenlands.blocks.BLBlockRegistry$8.func_149651_a(BLBlockRegistry.java)
at net.minecraft.client.renderer.texture.TextureMap.func_110573_f(TextureMap.java:335)
at net.minecraft.client.renderer.texture.TextureMap.(TextureMap.java:62)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:540)

-- Initialization --
Details:
Stacktrace:
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:878)
at net.minecraft.client.main.Main.main(SourceFile:148)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at weatherpony.pml.premain.ReplacementMainThread.run(ReplacementMainThread.java:104)

-- System Details --
Details:
Minecraft Version: 1.7.10
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 6064564208 bytes (5783 MB) / 6407585792 bytes (6110 MB) up to 6407585792 bytes (6110 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx6G -Xms6G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP v9.05 FML v7.10.99.99 Minecraft Forge 10.13.4.1614 32 mods loaded, 32 mods active
States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored
UCH mcp{9.05} [Minecraft Coder Pack] (minecraft.jar)
UCH FML{7.10.99.99} [Forge Mod Loader] (forge-1.7.10-10.13.4.1614-1.7.10.jar)
UCH Forge{10.13.4.1614} [Minecraft Forge] (forge-1.7.10-10.13.4.1614-1.7.10.jar)
UCH CodeChickenCore{1.0.4.29} [CodeChicken Core] (minecraft.jar)
UCH NotEnoughItems{1.0.3.74} [Not Enough Items] (NotEnoughItems-1.7.10-1.0.3.74-universal.jar)
UCH debug{1.0} [debug] (denseores-1.6.2.jar)
UCH mcpml{10.1} [Partial Modification Loader [for Minecraft]] (PML_MinecraftApp.jar)
UCH battlegear2{1.7.10} [Mine & Blade Battlegear 2 - Bullseye] (1.7.10-MB_Battlegear2-Bullseye-1.0.8.3.jar)
UCH seasonsmod{pre-3.0beta13d5} [The Seasons Mod] ([1.7.10]TheSeasonsMod-pre-3.0beta13d5.jar)
UCH seasonsmodac{1.0} [Additional Seasons Content] ([1.7.10]TheSeasonsMod-pre-3.0beta13d5.jar)
UCH abyssalcraft{1.8.9} [AbyssalCraft] (AbyssalCraft-1.7.10-1.8.9.jar)
UCH antiidconflict{1.3.5} [Anti Id Conflict] (AntiIdConflict-LATEST-1.7.10.jar)
UCH antiqueatlas{4.2.4-1.7.10} [Antique Atlas] (antiqueatlas-4.2.4-1.7.10.jar)
UCH hud{1.1b} [Better HUD] (Better HUD by NukeDuck [1.7.10][1.1b].zip)
UCH BiomesOPlenty{2.1.0} [Biomes O' Plenty] (BiomesOPlenty-1.7.10-2.1.0.1826-universal.jar)
UCH chocolateQuest{1.0} [Chocolate Quest] (chocolateQuest-1.7.10-1.1d.jar)
UCH druidry{2016.8.10-1.7.10} [§2Druidry] (druidry(2016.8.10.2)(1.7.10).jar)
UCH Enchiridion{1.3} [Enchiridion] (Enchiridion 2-1.7.10-2.0.2a.jar)
UCH Enchiridion2{2.0.2a} [Enchiridion 2] (Enchiridion 2-1.7.10-2.0.2a.jar)
UCH etfuturum{1.4.1} [Et Futurum] (Et Futurum-1.4.1.jar)
UCH golems{1.20} [Extra Golems] (Extra-Golems[1.7.10]-1.20.jar)
UCH farlanders{1.2b} [The Farlanders] (farlanders-1.7.10-v1.2b.jar)
UCH FastCraft{1.21} [FastCraft] (fastcraft-1.21.jar)
UCH recipehandler{1.7.10} [NoMoreRecipeConflict] (NoMoreRecipeConflict-0.3(1.7.10).jar)
UCH Roguelike{1.3.6.3} [Roguelike Dungeons] (roguelike-1.7.10-1.3.6.3.jar)
UCH AS_Ruins{15.4} [Ruins Spawning System] (Ruins-1.7.10.jar)
UCH thebetweenlands{1.0.6-alpha} [The Betweenlands] (TheBetweenlands-1.0.6-alpha-universal.jar)
UCH erebus{0.4.7} [Erebus] (TheErebus-0.4.7.jar)
UCH TooMuchTime{2.4.0} [TooMuchTime] (TooMuchTime-1.7.10-2.4.0.B3-universal.jar)
UCH TwilightForest{2.3.7} [The Twilight Forest] (twilightforest-1.7.10-2.3.7.jar)
UCH weaponmod{v1.14.3} [Balkon's WeaponMod] (weaponmod-1.14.3.jar)
UCH denseores{1.0} [Dense Ores] (denseores-1.6.2.jar)
GL info: ' Vendor: 'ATI Technologies Inc.' Version: '4.5.14008 Compatibility Profile Context 21.19.137.1' Renderer: 'AMD Radeon R7 200 Series'
Launched Version: 1.7.10-Forge10.13.4.1614-1.7.10
LWJGL: 2.9.1
OpenGL: AMD Radeon R7 200 Series GL version 4.5.14008 Compatibility Profile Context 21.19.137.1, ATI Technologies Inc.
GL Caps: Using GL 1.3 multitexturing.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Anisotropic filtering is supported and maximum anisotropy is 16.
Shaders are available because OpenGL 2.1 is supported.

Is Modded: Definitely; Client brand changed to 'fml,forge,pml'
Type: Client (map_client.txt)
Resource Packs: [AntiqueAtlasExtra.zip, John Smith Legacy 1.7.10 v1.2.24.zip]
Current Language: English (US)
Profiler Position: N/A (disabled)
Vec3 Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Anisotropic Filtering: Off (1)

Hmm, the Seasons Mod seems to generate code that attemps to access our code somehow. That's not our responsibility or something we can fix on our side really.