In lines 6-8, the wind suddenly becomes some sort of knife-wielding mugger:
[… the] wind wielded Blade-light, luminous black and emerald, Flexing like the lens of a mad eye. (6-8)
But what exactly is Hughes talking about here? Well, imagine some sunlight shining through on an otherwise cloudy day. The wind is blowing and moving the clouds around, causing the light to shift strangely, wildly—like the eye of a mad man. That might be what's going on here.
But what makes the blade light "luminous black and emerald"? Is this just a surreal touch, or effects caused by the interplay of shade and light? However you interpret these lines, one thing is pretty clear: this wind is some dangerous stuff. It even seems to be able to weaponize light, which just further symbolizes its awesome power.