Darkhax-Minecraft/Bookshelf#35 (comment) To simplify this issue post, the orignal post is linked above.

Client crashes if Bookshelf 251 is used along with Dark Utilities 1.1.0.38 for 1.9.4 This is due to Bookshelf having recently been updated, but Dark Utilities not being updated along with the API.

Crash report is located here: http://pastebin.com/t3Lp3aNw

Dependency call causing the issue is located here: https://github.com/Darkhax-Minecraft/Dark-Utilities/blob/master/build.gradle#L67

Already noticed this, dropped the ball on dependency management. Already fixed in my local branch of the project, just waiting a bit before uploading to CurseForge.

Fixed by 95a2b09

Also, no specific version of Bookshelf API is specified for use with the 1.1.0.38 version of Dark Utilities.