Way Of The Wicked - The Fall of Talingarde
Eye of Hatred
The Second Eye of Vetra-Kali
This jewel at first appears to be nothing more than an exquisite emerald worth at least 20,000 gp. Only if the jewel is steeped in the blood of a sentient creature does it reveal its true nature. The Eye of Hatred was the magical focus used to dedicate the Horn of Abaddon to the Four Horseman. It is thus sensitive to any outside interference. The Eye of Hatred pulses whenever any divine magic of Mitran origin is used within the Horn of Abaddon. The Eye is also a critical component of the ritual to destroy the Silver Seal and return Vetra-Kali to the prime material plane.
If all three of the Eyes of Vetra-Kali are united in the statue of Vetra-Kali in the Sanctum, then the Eye of Hatred not only pulses when such magic is used but immediately directs the Eye of Vigilance to show that magic being used.