Pascha
When the priest and deacon say their entrance prayers before the Paschal Vigil, they say them standing before the epitaphios (winding sheet). The order is the same as normal, except that in the usual beginning they do not say the prayer, "O Heavenly King...". This prayer is a hymn of Pentecost, and so will not be said again until that feast day.
During Bright Week—the week beginning on Pascha (Easter Sunday)—the ritual is the same, except that the usual beginning is entirely replaced by Paschal hymns.
At a Hierarchical celebration of the Paschal Divine Liturgy Axion Estin is replaced by the Irmos of the Ninth Ode of the Paschal Canon:
Shine! Shine! O new Jerusalem! The glory of the Lorth hath shown on thee. Exult now and be glad, O Zion. Be radiant, O pure Theotokos, in the Resurrection of thy Son.
Read more about this topic: Entrance Prayers