Mod talk:Obsidian Mod/@comment-4652667-20120710191301

Everytime i try to enter my world, it says "NPC Omnir is unknown, are you missing a mod?". I've tried to reload the mod but then it says "Modpack 'Obsidian Mod' is an outdated version (0.23.1). Rebuild it to use it with version 0.23.7

Press any key to continue"

How do i rebuild it? Help me please!