One of Krsna’s pastimes is to emanate, sustain, and reabsorb the material creation in periodic cycles, and this Krsna does in the persons of Brahma, Visnu, and Siva, who are called guna-avataras. Material nature acts in three ways or modes (gunas). When there is creation—construction, generation, procreation, etc.—material nature acts in the mode of passion (rajo-guna).When there is sustenance—maintenance, preservation, endurance, etc.—nature is working in the mode of goodness (sattva-guna). When there is destruction—decay, dissolution, devastation, etc.—nature acts in the mode of ignorance (tamo-guna).