In an effort to combat The Calamity, innkeepers from across the world have agreed to supply witches and wizards with free food. As you explore the Map, visit these locations to recharge Spell Energy by obtaining food. Various types of food restore different quantities of Spell Energy, and the availability of food you receive can be determined by particular features of the Inn, like the appearance of their rooftops.
In addition to collecting food, you can add Dark Detectors to an Inn to reveal rarer or more threatening Traces for a limited time. Find Inns at places like public art spaces, unique architecture, or public gathering places.
Getting food and replenishing Spell Energy
You will need plenty of Spell Energy to perform spell casts during magical encounters and for combat during Wizarding Challenges. If you’ve run out of Spell Energy, visit an Inn to keep your energy up.Tap on an Inn to enter, then trace the glyph on your screen to bring one of the dishes towards you. Spell Energy is added to your energy Vault after the food is revealed.
When you return to the Map, smoke piles out from the Inn to indicate you have to wait a few moments until you can get more food from the Inn.
Revealing higher threat Traces with Dark Detectors
Dark Detectors can be activated to reveal higher threat Traces near the Inn’s location for a limited time. You can get Dark Detectors as level up rewards or by purchasing one from Diagon Alley. Tap on the Dark Detector tab to place a Dark Detector to the Inn’s Amplifier (shown below). Your Code Name will be displayed beneath the Dark Detector you placed onto the Amplifier. 
A beacon appears above the Inn when a Dark Detector is active. Inns can have up to three Dark Detectors attached to them at a time. Placing more Dark Detectors on a single Inn multiplies the chances of revealing higher threat Traces.
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Harry Potter: Wizards Unite Game GUIDE
哈利波特：巫師聯盟