D&D 5E Magic item that ticks

[jgsugden]

You've accidentally ventured into a nifty space in my campaign history.

The thing is a solid metal box with a lead interior lining. There is no obvious way to open the box without breaking it. Someone has enchanted the interior of it with two Magic Mouths. The first emits a ticking sound every second. The second triggers if light reaches the interior of the box and says, "2 mile blast radius. Initiating Doomsday Event." 6. 5. 4. 3. 2. 1. They've also cast Nystul's Magic Aura so that the Magic Mouth spells appear to be evocation magic.

Credit to a former player that did something similar over and over and left them all over my campaign world as pranks.

 

[Paul Farquhar]

I think I will go with something like this:

Startclock Amulet

Wondrous item, very rare (requires attunement)

While you wear this amulet, you can press the button to cast the Haste spell on yourself as a bonus action. No concentration is required to maintain the spell. Whist the spell is active the amulet lets out a loud ticking that causes you to automatically fail any stealth checks. Once this property is used, it can't be used again until the next dawn.