In the Tyranny of Dragons campaigns, there are magic items called Dragon Masks.
They also appear in this supplement (p. 4).
In particular, I'm interested to know how this property works:
Dragon Sight. You gain darkvision out to 60 feet, or to an additional 60 feet if you already have that sense. Once per day, you can gain blindsight out to 30 feet for 5 minutes.
So since you can only do it once a day and it only lasts 5 minutes, it is something you must activate, right? But it doesn't explain how. In particular, what is the action economy cost for this? Does it cost an action? Is it an object interaction? Do you "just do it" like with a fighter's Action Surge?
I'm hoping there's something I've missed, or perhaps some generic rule somewhere that says something along the lines of "if it doesn't say, it's an action" or "if it doesn't say, you just do it".