The Tiger Widow is a giant spider from Ninjago: Masters of Spinjitzu.
The Tiger Widow inhabits Tiger Widow Island, and secretes a powerful venom. A small amount of this venom is enough to kill a human being, and it is the only substance known to be capable of weakening a Djinn, such as Nadakhan. Captain Soto and his crew used the venom against Nadakhan in their final battle, weakening him enough that Soto was able to trap him inside the Teapot of Tyrahn. With their leader imprisoned, Nadakhan's Sky Pirates were overcome by the rival pirate crew and banished across the Sixteen Realms.
After Nadakhan escaped in the present day, the Ninja learned of the means of his previous defeat from Soto, who had magically been restored to life some time previously.