Heralds of the Old Gods
The red-ribbon corset was recovered by Aubrey from Mariane's corpse. Mariane was able to use it to lay down difficult terrain, obscure enemy vision, entangle her foes, and drain life force from enemies. Mariane said that she had found the corset in one of her excursions across the world searching for magical artifacts, and that it was important to her because she was searching for some way to recover her magical power.
So far, Aubrey hasn't been able to harness the full suite of powers from the corset. However, they have been able to (somewhat accidentally) convince it to let them escape enemies by growing giant ribbony legs. The corset manifests its powers by extending out long red ribbons that pulse with a blood-like liquid if ripped.