"Devoted to Lunaris" is a beneficial modifier you can encounter in Path of Exile. It appears in the Necropolis zone and replaces a Haunted modifier on the Lantern.
Here’s a breakdown of what you explained about Devoted to Lunaris:
Defeat Rare Monsters with any 7 of the following types of Devoted Modifiers
Devoted Modifier Chance atlas skill: The Lantern of Arimor has 10% increased chance for Devoted Modifiers. Devout Pursuit atlas notable: The Lantern of Arimor has 30% increased chance for Devoted Modifiers.