As an action, a spectral blade forms on the end of a quarterstaff you are holding and lasts for the duration. The weapon’s damage type changes to slashing and it becomes magical, if it isn’t already.
The spell ends if you dismiss it on your turn (no action required), if you cast it again, or if you end your turn without the scythe in your hand.
At higher levels
When you reach 9th level, you can make an attack with the blade as part of the same action to create it.