The Rite of AshkEnte is from the Discworld series by Terry Pratchett. After the Rite is cast, Death (or whomever is filling in for Death) is summoned. In theory he has to answer three questions, and must stay contained within the octagram. In actuality, Death does in fact have to appear, but is under no obligation to remain in the confines of the octagram, or to answer the questions.
The Rite of AshkEnte is usually performed by the wizards at Unseen University. There is a noticeable difference in the way generations of wizards cast the spell. Older generations prefer to dress up in dramatic ceremonial robes, waving staves, have exact placements of rams horns, skulls, baroque metalwork, heavy candles dribbling wax with octagons carved in them, and pints of goats blood in addition to much chanting and reading obscure texts.
The younger generation of magic-users, however, have discovered that the Rite may be performed just as well with three small bits of wood and 4 cc of mouse blood.
The founder of Unseen University, Alberto Malich, performed the Rite backwards and as a result was transported to Death's Domain, where he ended up serving as Death's butler.
To date, those who have been accidentally summoned by The Rite of AshkEnte are the Death of Rats, Susan Sto-Helit, and Mort. I cannot recall offhand if Rincewind was summoned or not with it in Eric or if that was a different spell.