1. Mikveh
A mikveh is a bath used for ritual purification in Judaism. It uses natural water and was commonly found in areas with Jewish communities. It remains an essential part of Jewish tradition today. This purification refers to ritual cleansing. Jews believed that immersing themselves in water would cleanse them of impurities. Gentiles converting to Judaism and those who had come into contact with impurities needed to immerse themselves in a mikveh to become ritually pure before entering the temple or Jerusalem.
In the New Testament, various methods of washing the whole body, hands, or feet are mentioned, which are similar to the mikveh. When John the Baptist baptized with water, he too had people fully immerse themselves. This wasn't his innovation but was done within the common understanding of Jewish tradition.
2. Caiaphas
Caiaphas is known as the son-in-law of Annas, implying he wasn't from a prominent family himself. The portrayal in this story, showing how someone with relatively pure faith becomes corrupted by worldly desires, is entirely fictional for the sake of the story. In contrast, it is historically accurate that High Priest Simon from Alexandria was King Herod's father-in-law and became High Priest because of his daughter. It's probable that he was the High Priest when Zechariah encountered the angel in the temple. I wanted to use Caiaphas to express the feeling of inadequacy Zechariah might have felt observing Simon.
Incidentally, the daughter of High Priest Simon, Mariamne II, had a son with King Herod named Herod Philip I. The daughter of Herod Philip I and Herodias was Salome, responsible for John the Baptist's execution. This family has significant connections to Zechariah in several ways.
