Design for Great Day — Alan Dean Foster

When a strange starship appears mysteriously on a distant alien world, bearing only a single human and his bee-like extraterrestrial companion, the powerful warlord of that world laughs at the stranger's preposterous demand: End an all-out war with an interstellar rival, or face devastating consequences. But James Lawson, emissary from an intergalactic federation of advanced race, means every word he says, and has the power to back them up--whatever the cost.