The Blade of Talzin is a sword emanating flaming green ichor, allowing it to withstand lightsaber attacks. Elsbeth uses it to fight Ahsoka, but is ultimately killed by it when Ahsoka takes it from her and delivers a dual slash to the Nightsister’s guts with her lightsaber and the Blade of Talzin. This feels appropriate, given how its previous owner met their fate.
The blade both belonged to and is named after Mother Talzin, the leader of the Nightsisters of Dathomir during the Clone Wars. It was Talzin who united all the Nightsisters into a single clan and proved a big enough threat to Darth Sidious for him to eventually want to eliminate her. As we saw in “The Clone Wars,” Talzin’s attempt to assassinate Count Dooku resulted in Grievous and his droid armies wiping out all the Nightsisters on Dathomir, but it was not enough to kill Talzin.
Instead, the Great Mother used her powers to restore her half-dead son Maul back to health, at the cost of her physical body. Then, in order to gain back her physical body, Talzin gained the allegiance of a cult that kidnapped people to steal their Living Force. After kidnapping Queen Julia of Bardotta to do the same, Talzin inadvertently drew the attention of Jedi Master Mace Windu and unsung hero Jar Jar Binks. Talzin fights Mace, using the cursed green blade, in a cool lightsaber fight. Despite her surprisingly good sword-fighting skills, Talzin was no match for the senator responsible for both Palpatine’s right to dictatorship and the saving of Grogu.
It seems that, no matter the situation, the Blade of Talzin is not really a gift but a harbinger of death.