is there a way to combine them? there's a very loose hint about putting them together... There are the fruit bones with a description of them making a strong component. Have them, wondering whether to sell or make a weapon...

The weapon dropped by Fruit Punch has to be combined with freshly harvested fruit bones to make a fruit bone dagger. The weapon dropped by Fuyaira has to be combined with mystical icicle to make frost thorn. The fruit bones are the special loot of Fruit Salad (tier 8 challenger unlocked by beating Fruit Punch 25x) and the icicle is the special loot of Odontos (tier 7 challenger unlocked by beating Fuyaira 25x).