When the grail is first seen by Perceval, it is carried in by a young lady:

A maiden accompanying the two young men was carrying a grail with her two hands; she was beautiful noble, and richly attired. After she had entered the hall carrying the grail the room was so brightly illumined that the candles lost their brilliance like starts and the moon when the sun rises [....] The grail, which was introduced first, was of fine pure gold. Set in the grail were precious stones of many kinds, the best and costliest to be found in earth or sea: the grail's stones were finder than any others in the world, without any doubt. The grail passed by like the lance; they passed in front of the bed and into another chamber. (420-1)
Later on, he finds out more about the grail, which has properties that sustain the life of the wounded king's father:
[.... T]he rich Fisher King, I believe, is the son of the king who is served from the grail. And do not imagine he is served pike or lamprey or salmon. A single host that is brought to him in that grail sustains and brings comfort to that holy man - such is the holiness of the grail. And he is so holy that his life is sustained by nothing more than the host that comes in the grail. He has lived for twelve years like this, without ever leaving the room into which you saw the grail enter. (460)
Because De Troyes' narrative does not conclude Perceval's adventures, this is the last time the grail is discussed in the book.

Selections from Chrétien De Troyes' Arthurian Romances. Translated by Carleton W. Carroll