when would the priest enter the holy of holies
Holy of Holies The Holy of Holies was covered by a veil, and no one was allowed to enter except the High Priest, and even he could only enter once a year on Yom Kippur (the day of atonement), to offer the blood of sacrifice and incense before the mercy seat. The Bible reports that in the wilderness, on the day that the tabernacle was first raised up, the cloud of the Lord covered the tabernacle (Exodus 40:33-40:34). There are other times that this was recorded, and instructions were given that the Lord would appear in the cloud upon the mercy seat (kapporet), and at that time the priests should not enter into the tabernacle (Leviticus 16:2). According to the Hebrew Bible, the Holy of Holies contained the Ark of the Covenant with representation of Cherubim. Upon completion of the dedication of the Tabernacle, the Voice of God spoke to Moses "from between the Cherubim" (Numbers 7:89).
Litany of the Saints The Litany of Saints is used prominently at the Easter Vigil, the Mass celebrated on the night before Easter Day. At this Mass, adults who have chosen to become Catholic receive the Sacraments of Initiation in the form of Baptism, or simple Reception, with Confirmation and Holy Communion. Following the readings from Scripture and just before the actual rite of baptism or confirmation, the Litany of Saints is sung. Even if there is no-one to be baptized, the Litany may be sung for the blessing of holy water in the font. But if the font is not blessed (i.e. holy water is blessed in a simple container on the sanctuary), the Litany is not used.