A grand celebration that brings together the folk art forms of Kerala, Athachamayam marks the beginning of the ten-day festival of Onam. Athachamayam commemorates the victory of the king of Kochi and is usually celebrated in August/September, when a spectacular procession representing the king and his entourage is taken out. Several floats depicting scenes from epics like Ramayana and Mahabharata, caparisoned elephants, folk art forms and musical ensembles accompany this procession. The ceremony begins by lighting a lamp, a symbolic gesture performed by a priest. The participants are usually dressed in silk ensembles that include a yellow kurta and pyjama for men, and pevada davani or sarees for women. People also don colourful and elaborate masks to complement their attire.

Of particular note are dance forms like theyyam, in which dancers dressed in elaborate skirts and huge headgear perform. Legend has it that a benevolent king, Mahabali, once ruled the region, whose subjects started to worship him. This angered the gods as the king was a demon and they killed him. Thus, the festival is celebrated to commemorate the king.