Serapis (, later form) or Sarapis (, earlier form, originally Demotic: "wsjr-ḥp," "Userhapi" "Osiris-Apis") is a Graeco-Egyptian deity. The cult of Serapis was pushed forward during the third century BC on the orders of Greek Pharaoh Ptolemy I Soter of the Ptolemaic Kingdom in Egypt as a means to unify the Greeks and Egyptians in his realm. A serapeum ( "serapeion") was any temple or religious precinct devoted to Serapis. The "cultus" of Serapis was spread as a matter of deliberate policy by the Ptolemaic kings, who also built the immense Serapeum of Alexandria. Serapis continued to increase in popularity during the Roman Empire, often replacing Osiris as the consort of Isis in temples outside Egypt.