Devotion dust is obtainable from the devotion rocks scattered around the Lumbridge Crater during the 2017 Valentine's Day event. Devotion dust can obtained by Mining and Smithing crashed devotion rocks, or taken in groups of 500 from the crate of devotion dust near Wizard Deedit. There is no limit to the amount you can take from the crate. The dust can be used to fix the broken unity machine or fed to the Devotion Sprites.