In Wheel of Time book 8, The Path of Daggers, Elayne is investigating the ter'angreal found in Ebou Dar when:
And then there was the crimson rod that felt hot. Hot, in a way.
Sitting on the edge of her bed at an inn called The Wild Boar, she examined the smooth rod by the light of two polished brass lamps. Wrist-thick and a foot long, it looked like stone, but felt firm rather than hard. She was alone; since the helmet, she had tried to do her studying away from the others. The heat of the rod made her think of Fire...
Blinking, she opened her eyes and sat up in the bed. Sunlight streamed in at the window. She was in her shift, and Nynaeve, fully dressed, stood frowning down at her. Aviendha and Birgitte were watching from beside the door.
"What happened?" Elayne demanded, and Nynaeve shook her head grimly.
"You don’t want to know." Her lips twitched.
Aviendha’s face gave away nothing. Birgitte’s mouth might have been a little tight, but the strongest emotion Elayne felt from her was a combination of relief and — hilarity! The woman was doing her utmost not to roll on the floor laughing!
The worst of it was, no one would tell what had happened. What she had said, or done; she was sure it was that, by the quickly hidden grins she saw, from Kinswomen and Windfinders as well as sisters. But no one would tell her! After that, she decided to leave studying the ter’angreal to somewhere more comfortable than a inn. Somewhere definitely more private!
Do we ever find out what this crimson rod ter'angreal does? Perhaps in a chapter from Nynaeve's or someone else's point of view? Or does it remain forever an embarrassing secret?