The Sen Ennis were a group who were formed out of the Ennis and the Nol-Ennis in 2373.
The two groups brought their war to a close as Opaka Sulan's teachings and religious meditations proved more popular. Golin Shel-la and Zlangco agreed that the two groups needed to be merged into one, leading to the creation of the Sen Ennis. Less than a month later, the Ascendant Raiq destroyed the satellite network that had resurrected and trapped the Ennis and the Nol-Ennis, as a reward for Opaka treating her when Raiq was injured. The Sen Ennis soon left the moon and settled on the planet Ee, becoming known as a new religious movement. (DS9 novel: Rising Son)
In 2376, a Founder sent Vannis to the moon of the Sen Ennis as part of Odo's investigation into the Ascendants. (DS9 - Worlds of DS9 novel: The Dominion: Olympus Descending)