The Yashts are a set of twenty one hymns, each addressed to a single yazata, a being worthy of veneration in the Zoroastrian system, and together they are the most narratively vivid part of the Avesta. Where the Yasna is defined by ritual function and the Vendidad by legal procedure, the Yashts read as praise poetry with embedded myth: they describe the deeds, appearance and power of their subject, and several preserve stories found nowhere else in the surviving Avesta.
The best known examples include the Mihr Yasht, addressed to Mithra as a guardian of covenants and oaths, the Aban Yasht, addressed to the waters and to the goddess Anahita, and the Bahram Yasht, addressed to Verethragna, a being associated with victory. Because each Yasht was composed and transmitted somewhat independently before being gathered into a single collection, they vary considerably in length, poetic quality and apparent age, and a few are thought to preserve pre-Zoroastrian material that was reworked to fit the tradition's theology rather than composed fresh within it.
Individual Yashts remain in active devotional use, recited on the calendar day associated with their yazata, which keeps them closer to living practice than some of the Avesta's more purely liturgical material.