The Double-Bladed Scimitar can be found in Eberron: Rising from the Last War, page 21.
This magic weapon has a dull, rusty color or has veins of ruidium running through it. While this weapon is on your person, you gain the following benefits:
A creature you hit with this weapon takes an extra 2d6 psychic damage.
When you roll a 1 on an attack roll made with this weapon, you must make a DC 20 Charisma saving throw. On a failed save, you gain 1 level of exhaustion. If you are not already suffering from ruidium corruption, you become corrupted when you fail this save.
If the Apotheon is killed or redeemed, all the ruidium in Exandria is destroyed instantly, and a ruidium weapon becomes a +2 weapon.
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.