Pack of Revisibility Bombs
A pack of revisibility bombs typically includes 1d3 + 3 fist-sized bombs when found. You can use an action to throw a bomb at a point that you can see within 60 feet of you. The bomb explodes at the point where it impacts, destroying the bomb and releasing a dispelling vapor in a cloud around it. When the bomb explodes, each creature within 30 feet of it must make a DC 20 Dexterity saving throw. On a failed save, the creature becomes visible if it isn't already, and can't become invisible for 1 minute. Objects within the area that aren't being worn or carried automatically become visible if they're invisible and can't become invisible for 1 minute.
"Did you hear that?" hissed the guard captain. Her hand shot to the blade and satchel at her side. The other two guards noiselessly nodded at her. Footsteps from the stairwell. Coming toward them. As the three guards stood at the ready, their weapons drawn, anticipation turned to anxiety as the sound of steps grew quiet. Suddenly, a sharp clink broke the silence like ice into frigid water. The sound of metal, like a blade, scraped against the stone walls to the side of the room around them. "Show yourselves!" shouted the captain. Her hand, already in a fist, opened to reveal a small, glowing orb. She threw the sphere into the wall where the sound had come from and watched as it shattered against the stone. Billowing vapor filled the space, and a moment later, there were six people in that room, instead of three.