Write about a world like ours, but missing a huge aspect that we take for granted. Eg. Light, speech, recorded history, etc.
Describe this other world and evince the mood that this world effuses. Try to use concrete descriptions (so don't just piece together a bunch of emotional adjectives in a sentence). As Chekov says, don't tell me the moon is shining, show me the glint of light on broken glass. Prose, poetry; any format is fine, but again, you shouldn't have to state what feeling it is you're evoking. Poetry isn't an excuse!
