Antonio -- Although you probably won't use it very often, the word жрец -- "a priest in ancient paganism" -- comes from the same root as the verb (по)жертвовать, "to sacrifice." So, the жертва was the animal (or person!) tied up on the altar, and the жрец was THIS guy:



P.S. However, священник is the correct word for "priest" in the modern sense, whether you mean Russian Orthodox, Catholic, Buddhist, etc.