Pwyll employed one of these items to overcome Gwawl, and Perseus used his to carry the head of the Medusa.
In Japanese myth, the hero Yakato-takeru is given the sword Kusanagi and one of these objects by his aunt, and with the help of this object overcomes the king of Sagamu. In Chinese myth, Shennong, who had a crystal stomach, was said to possess two of these objects for two different types of herbs. In Russian folklore, a man named Ivan the Soldier was able to obtain a magical object of this type after trapping three demons in his knapsack; that object would provide him with anything he wanted, and Ivan also used this object to trap Death. Along with winged sandals and the helmet of invisibility, Perseus received a magic item of this kind from the nymphs. Pwyll employed one of these items to overcome Gwawl, and Perseus used his to carry the head of the Medusa. For ten points, identify this type of common object, one of which belonging to Aeolus contained the winds.
In Japanese myth, the hero Yakato-takeru is given the sword Kusanagi and one of these objects by his aunt, and with the help of this object overcomes the king of Sagamu.
{bag} or {pouch} or {sack} [or any other synonyms]