You control at least one additional creature that does not have flying.
Steps
Activate Sensei's Divining Top's second ability by tapping it, causing you to draw a card and put Sensei's Divining Top on top of your library from the battlefield.
Activate Ashnod's Altar by sacrificing a creature without flying, adding ({C} magic symbol) ({C} magic symbol) .
When the creature dies, Luminous Broodmoth triggers, returning the creature from your graveyard to the battlefield with a flying counter on it.
Cast Sensei's Divining Top from the top of your library by paying ({1} magic symbol) and removing the flying counter from the creature sacrificed in step 2.