Versions

Betweenlands version:

Latest

Forge version:

Latest

Singleplayer or Multiplayer:

SP

Installed mods:

https://www.curseforge.com/minecraft/modpacks/minecraft-eternal

Also added

optifine
Redstone Arsenal
Blood Magic
Animus
Genetics reborn
Apotheosis
Serene Seasons
Youngs better caves
Save My Stronghold!
Draconic evolution
MmmMmmMmmMmm
PSI
Super sound muffler revived
Torch master
Better advancements
Enivonemntal tech
Ender io energy
Morph-o-Tool
Pretty beaches
Unlimited Chisel Works
Potion icon remover
immersive railroading
Snow! Real Magic!
(And library mods needed for these mods not on the list)

Link to full crash log

https://gist.github.com/EAGBCD/38d045127cd16eb2ac45bc658d02480a

Description of the problem crash on start up

How to reproduce:

1. Prest start game
2. Wait till the end of step 2 on the forge thing
3. Crash

Expected result:

Game open good

Actual result:

Game not open

Pictures:

You've run out of potion IDs. Adding more mods to large modpacks that already push limits will likely cause such issues. You can try using https://www.curseforge.com/minecraft/mc-mods/jeid, however be warned that this can potentially corrupt worlds, so make backups.