After being gone from Acronymia for a few weeks, Tessa returned. The timewalker was now over a hundred years old, frail, and suffering from dementia. Though sometimes she appeared lucid enough to remember her age, at other times she seemed to to be reliving the time when she was plotting to kill Alek.
Of course, Calublufiok couldn't resist trying to get those bracelets from her. After a failed attempt to drug her, he finally just came out and openly challenged her to combat, with an implied threat to destroy the Taverna if she didn't accept.
Cal won the fight and killed a perfectly harmless little old lady. Immediately the bracelets began burning off mana at a furious rate. If Cal didn't act quickly, they would soon be completely mundane bits of jewellery. He ate Tessa's brain to gain her knowledge of the bracelets, and discovered that they should have cast a true resurrection as a contingency. He tried to capture Tessa's soul to keep that from happening, but the soul capture was unsuccessful. However, she did not resurrect.
He also noticed that her brain was strangely burnt in places which didn't seem to correspond to the damage she'd been dealt in combat, but was in too much of a hurry to secure the bracelets to ponder the matter. He finally recovered the memory of Tessa's first contact with the bracelets and put them on.
Tessa spent years designing the trap. She considered using a simulacrum, but knew that Cal would be able to detect it. So when she reached the end of her life and was ready to sacrifice it, she laid her plans, setting the spells in place, and then stepping through a portal to Acronymia. Once there, she burnt out her own memory of what she'd done as well as the details of how to control the bracelets. In essence, she gave herself dementia, knowing that Cal would never be able to resist the bait.
Had he not put on the bracelets, they would have burned themselves out. But he did. She knew he would. And that's why she arranged to have her soul bind itself to the bracelets.
For now, Cal seems to have control over the bracelets, but he's also become dependant on them. If he removes them, his ability to cast spells goes with them. And meanwhile, Tessa remains within the bracelets. Watching. Waiting.