Introduction
Zairicha is one of the six chief daevas of Zoroastrianism, opposed to the Amesha Spenta Ameretat, "Immortality". Where Ameretat represents the eternal life promised to the righteous, Zairicha represents its opposite: poison, decay and death.
Opposition to immortality
As the daeva paired against Ameretat, Zairicha is associated with poison specifically, and more broadly with the processes of decay and death that stand as the ultimate opposite of the deathless, eternal life Ameretat represents and that the righteous are promised at the final resurrection.
Paired with Taurvi
Zairicha is generally named alongside Taurvi, the daeva opposed to Haurvatat (Wholeness/Health), the two together representing the full range of bodily harm, from sickness and injury (Taurvi) to poison and death itself (Zairicha), that Angra Mainyu introduced into the world.