Seeing how powerful the magma horn is, you can see that it can only be used once, and very wisely! It is often described as a pine tree branch with hot embers on it. To make a magma horn, you bake a cookie, throw it in the fire, eat it.. get a pine tree branch, stick it in the fire for 20 minutes. Pull it out, slam it and bam. Universe ends in a spectacular display of boom.