The Yklwa can be found in Tomb of Annihilation, page 32.
This magic weapon grants a +1 bonus to attack and damage rolls made with it. While holding it, you can take a Bonus Action to cause it to shed Bright Light in a 30-foot radius and Dim Light for an additional 30 feet. You can extinguish the light as a Bonus Action.
The weapon has 4 charges. You can take a Reaction immediately after being hit by an attack roll to expend 1 of the weapon's charges and force the attacker to make a DC 15 Constitution saving throw. On a failed save, the attacker has the Blinded condition until the end of its next turn. The weapon regains 1d4 expended charges daily at dawn.
A yklwa (pronounced YICK-ul-wah) is a simple melee weapon that is the traditional weapon of Chultan warriors. A yklwa consists of a 3-foot wooden shaft with a steel or stone blade up to 18 inches long. Although it has the thrown weapon property, the yklwa is not well balanced for throwing.
If a weapon has the thrown property, you can throw the weapon to make a ranged attack. If the weapon is a melee weapon, you use the same ability modifier for that attack roll and damage roll that you would use for a melee attack with the weapon. For example, if you throw a handaxe, you use your Strength, but if you throw a dagger, you can use either your Strength or your Dexterity, since the dagger has the finesse property.