Kalman has little idea what the mervyl are, but they sound to him like something his friend Búkk mentioned before leaving for Tharâkh Bazân.
'I don't know what these creatures are, ${PLAYER} -- this is the first I've seen or heard of them, though perhaps they are related to the merrevail -- but I am certain that their presence here in Khazad-dûm bodes only ill.
'Perhaps Búkk may be of help to us. I seem to recall him mentioning something about these creatures, and I suspect that he may have encountered them again on his way to Tharâkh Bazân. Speak with Búkk and find out what information he may have.'
Búkk can be found in Tharâkh Bazân, the gardens to the east.
Kalman recommends that you speak with his friend Búkk about the mervyl.
Arnod can be found at the camp in Tharâkh Bazân, the gardens east of the Door to the Clouds.
Búkk recommends speaking with Arnod, who has studied the maps and history of Khazad-dûm, about where to begin searching for mervyl.