A starfury staff is an upgraded version of the starfire staff. The process of upgrading involves a starborn diamond. It could also be won from the Squeal of Fortune as a "Rare" reward. However, the ability to win it expired on the 7th of May. It is possible to receive one from a sparkling clover necklace.
As with any other staff, damage values depend on the spell used. The Magic level can be changed by right-clicking on the staff while unequipped and selecting "Change".
If this staff is lost, Diango can replace it for a fee which varies depending on which tier you are able to use; e.g., if you can use the highest tier, he will charge 50,000 coins to replace it.