Below is a walkthrough for the Knife to Meet You side quest in Tiny Tina’s Wonderlands. To obtain this quest, speak with Bach Stahb in the Overworld.
Reach ruin
When facing Bach Stahb, follow the path to the right then swing north to find the ruins. Fight through two encounters (making sure to melee an enemy) then retrieve the shrine piece for Mool Ah.
Return to Mool Ah and interact with him to complete the quest.