The Double-Bladed Scimitar can be found in Eberron: Rising from the Last War, page 21.
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.
If you attack with a double-bladed scimitar as part of the Attack action on your turn, you can use a bonus action immediately after to make a melee attack with it. This attack deals 1d4 slashing damage on a hit, instead of 2d4.
This weapon requires two hands to use. This property is relevant only when you attack with the weapon, not when you simply hold it.