Garhartra is the Guestmaster of Krull. He has the job of welcoming visitors to Krull and assuring them that their every wish will be granted, especially in the matter of preserved echinoderms. It is his pleasant task to ensure that their stay on Krull is as enjoyable as possible, and if they want anything they have only to ask.
This speech precedes the second part of his speech, in which the definite prospect of ritual sacrifice is raised. Some guests have been known to behave badly on hearing this, which is why Garhartra is a fully-qualified wizard with an armoury of defensive spells at his fingertips. He really doesn't like using them, but sometimes an unruly guest might let the ich food and drink go to his head somewhat and need to be restrained - always acting in self-defence and by using a minimum of physical force, as anything more would be unseemly conduct towards a honoured guest.
He welcomed Rincewind and Twoflower to Krull, before informing them that they will be sacrificed to ensure the success of the Potent Voyager's mission over the rim of Discworld to determine the sex of the great turtle.