Iriel learned that Hellica, Matre Superior of the Honored Matres, who chose not to merge with the New Sisterhood, was going to use four Obliterator super-weapons to destroy the planet Chapterhouse. She and a handful of others managed to fold space away from Gammu in a lightly defended no-ship, and warn Murbella, Mother Commander of the Sisterhood, before Hellica's forces reached Chapterhouse.
Murbella, and daughter, Janess Idaho, raised a quick defense of Chapterhouse by placing hundreds of Richesean mines outside of the atmosphere of the planet. When the Guild Heighliners came out of fold space in that designated staging area, Murbella warned the Guild that they had been found out, and that the Sisterhood were aware of the Matres plans.
Murbella worked out a deal that the Guild would allow the Sisterhood to come aboard the heighliner and duel to the death with the Matres aboard their ships. Although Iriel had only recovered from the injuries she had sustained fleeing from Gammu, she took place in the Matre payback attack. The tally was that the Sisterhood prevailed; but five sisters died, including Iriel.