Ketty Muttart (ケティ・ムッタート) was a merchant and a member of the Witch Cult.
Ketty is a man with brown hair and green eyes.
Ketty is first seen at Arc 3 as a merchant, He is the one that introduces Natsuki Subaru to a drunk Otto Suwen, a merchant he is an acquaintance, Otto at the time was in desperate need to sell his oil and accepted Subaru's offer to take him to Roswaal's Domain at the time.
Later on, it is revealed that he is one of the fingers of Petelgeuse Romanee-Conti, Subaru uses this knowledge to spread disinformation amongst the merchants, knowing that Ketty would fall for it and report incorrect info for the members of the cult. After he had fallen for Subaru's trick, he was arrested, the magic formula that allowed him to become a finger and explode upon a dangerous situation was removed by Ferris and he was taken in for questioning about Witch Cult Activity, never to be seen again. The last mention of him was when Otto mentions that he was disappointed with Ketty after knowing he was a member of the witch cult.