When I made Aviendha's costume a few months ago, I intended to make the dagger ter'angreal that wards against the Shadow that she likes so much. Last weekend I finally did so, along with rebeading her necklace with silver thread.
The dagger is described as:
Aviendha fondled something she had retrieved from her belt pouch, a small dagger with a rough hilt of deerhorn wrapped in gold wire. It was also a ter'angreal, though Elayne had not been able to puzzle out what it did before pregnancy forced a halt to such studies. She had not known her sister was carrying the thing. Aviendha's eyes were almost dreamy as she stared at it. "Why does that fascinate you so?" Elayne asked. This was not the first time she had seen the other woman absorbed in that knife. Aviendha gave a start and blinked at the dagger in her hands. The iron blade—it looked like iron, at least, and felt almost like iron—had never been sharpened so far as Elayne could tell and was little longer than her palm, though wide in proportion. Even the point was too blunt for stabbing.
Knife of Dreams, A Different Skill
Aviendha's outfit is now complete.