Oh My Goddess! Vol 42

From the Dark Horse edition

Mokkurkalfi, Hell's mistress of machines, is the next door warden Keiichi and the goddesses must pass. With her mechanical skills, she's the natural opponent of Skuld... but unlike her, Mokkurkalfi has no love for her inventions, instead setting them against each other viciously, to retain only those strongest in battle! Will so ruthless an approach to robots be the defeat of the youngest goddess... and of them all?

Source: Anime News Network Encyclopedia