Sling of Warning

Ammo: sling bullet [5.5e]

As long as this weapon is within your reach and you are attuned to it, you and allies within 30 feet of you gain the following benefits.

Alarm: The weapon magically awakens each subject who is sleeping naturally when combat begins. This benefit doesn't wake a subject from magically induced sleep.

Supernatural Readiness: Each subject has Advantage on its Initiative rolls.

Slow (Mastery): If you hit a creature with this weapon and deal damage to it, you can reduce its Speed by 10 feet until the start of your next turn. If the creature is hit more than once by weapons that have this property, the Speed reduction doesn't exceed 10 feet.

Ammunition: You can use a weapon that has the Ammunition property to make a ranged attack only if you have ammunition to fire from it. The type of ammunition required is specified with the weapon's range. Each attack expends one piece of ammunition. Drawing the ammunition is part of the attack (you need a free hand to load a one-handed weapon). After a fight, you can spend 1 minute to recover half the ammunition (round down) you used in the fight; the rest is lost.

Proficiency: simple, sling Source: Dungeon Master's Guide (2024) p. 324