While the iconography associated with the body of the deceased king -i.e., the mummy, coffin, and sarcophagus- was associated primarily with Osiris, the imagery of royal tomb decoration as seen throughout New Kingdom monuments is primarily linked with the king’s assimilation with the sun god. This assimilation or fusion involves the king’s cyclic travel with Re into, through, and out of the netherworld regions in continuing renewal and rebirth. The imagery of solar assimilation may be varied, however. On the one hand the god-king is said to ride alongside Re in the celestial boat of the sun god and to act as a judge in the realm of Re, while on the other hand he is clearly said to be one with the solar god. Both are depicted iconographically, the latter when the name of Ramsses III is written within a solar image in that god’s tomb.
— The Complete Gods and Goddesses of Ancient Egypt By Richard H. Wilkinson