Probably bvecause it adds new biomes, world gen with abyssalcraft locks up before the world can complete generation. Here's my FML log.

Removed Abyssalcraft and was able to proceed with world creation

Thanks for the bug report, have added it to the new bugs thread at https://www.reddit.com/r/openterraingen/comments/67uzha/mod_compatibility_bugs_report_them_here/

This should be solved with v16, https://minecraft.curseforge.com/projects/open-terrain-generator. Closing this issue, if v16 doesn't fix this then feel free to re-open.

Hi PG85, the update does fix the crash, but does the update allow for the Abyssalcraft biome generation as the mod requires? I pregenerated a few worlds and do not see the biomes the mod creates - Darklands, Coralium Infested Swamp, etc. Thanks for looking in!