The centre of the Triduum, and by the church's own account the mother of all vigils, is the Easter Vigil, kept in the night between Holy Saturday and Easter Sunday. Its shape is among the most archaic things in Christian worship. It begins outside, in darkness, with the kindling and blessing of new fire; the paschal candle is lit from it and carried into the unlit church, the light passing candle to candle through the congregation; the deacon then sings the Exsultet, the long proclamation of the night itself. There follows an extended vigil of readings that walks through the whole sweep of scripture, creation, the crossing of the sea, the prophets, before the first Easter alleluia.
The night was from early centuries the preferred moment for baptism, the candidates descending into the water as the church passed from death to life, and the modern rite keeps that inheritance: the font is blessed, catechumens are baptised, and the whole assembly renews its baptismal promises. The vigil's modern prominence is itself a piece of history. By the medieval period it had drifted to Saturday morning, its symbolism of light in darkness inverted; Pius XII restored it to the night in the 1950s, ahead of the wider reforms, and the restored night vigil now stands as the single most solemn liturgy of the Christian year.