The Candelabrum of Invocation is a unique item required to perform the invocation ritual, which in turn is required to ascend. Vlad the Impaler carries the Candelabrum at the top level of his tower, located in the middle of Gehennom. Before being identified, it appears as a simple candelabrum.
In order to light the Candelabrum, you must first attach seven candles to it. Do this by applying candles while carrying the Candelabrum. The Candelabrum provides a light radius slightly larger than an ordinary lamp, so it is recommended that you minimize the time the Candelabrum is needlessly lit. You can use the extra light radius for expert jumping on Astral to great effect.
Attaching candles to the Candelabrum removes their weight from your inventory, so there is a small advantage to applying candles right away.
Faustus: Come on Mephistopheles. What shall we do?
Mephistopheles: Nay, I know not. We shall be cursed with bell,
book, and candle.
Faustus: How? Bell, book, and candle, candle, book, and bell,
Forward and backward, to curse Faustus to hell.
Anon you shall hear a hog grunt, a calf bleat, and an ass bray,
Because it is Saint Peter's holy day.
(Enter all the Friars to sing the dirge)
Bell, Book and Candle is a Catholic excommunication ritual, although in the source code the candelabrum is sometimes referred to as a menorah, the seven branched candelabrum of Jewish ritual.