A bow made from starlight ore, with an embedded starborn diamond.
Starfury bows are special in that they have four different leveled versions of themselves (level 1, level 20, level 40 and level 60). You can transform your weapon into one of these alternate versions by right-clicking it in your inventory and choosing "change".
You will need a starfire bow and starborn diamonds. Starborn diamonds can be won on the Squeal of Fortune or found through skilling or slaying creatures.
To make the starfury bow, take a starfire bow and the required number of starborn diamonds to Ivar in the Artisans Workshop and he will smith a starfury bow for you.
Making these bows will provide you with 250 Mining XP.
Speaking to Ivar will take all of your starlight bows and starborn diamonds from your inventory and bank. If you do not have enough of these to make the related weapon, the items will still be taken and you will be granted XP based on the items alone. Starlight ore will provide 5 Mining XP and starborn diamonds will give 2000.
If lost, the bow can be reclaimed from Diango for a price.