Merrok was Enabran Tain's arch-nemesis; he backed the Klingon-Romulan alliance and subsequent exchange of cloaking technology with the Klingons in an attempt to have the two empires 'contain' the Cardassians. Later he was a persistent thorn in the side of Cardassian/Romulan negotiations to exchange advanced Cardassian weaponry for cloaking technology.
Merrok was a keen gardener which would be his downfall. Tain organised an Obsidian Order operation working with the Romulan Senator Pelek. Tain had Elim Garak cultivate Edosian Orchids which were then pollinated with the White Star of Night to create a toxic bloom, and at Pelek's invitation Merrok arranged to have some of the rare orchids transplanted to his garden. Unaware of their potentially deadly characteristics, Merrok died the next day after inhaling their toxins. (DS9 novel: A Stitch in Time)