Tales of Tolgard
Xeg-yi are creatures from the Plane of Negative Energy. They are summoned by spellcasters and used as guardians of magical treasures.
They appear as 5-foot diameter spheres with six 5-foot long tendrils protruding around its body. The xag-ya has two dull metallic eyes set in the center of its body.
The xeg-yi attacks using its tendrils to touch an opponent or fire a blast of energy at a foe. They deal cold damage, destroy combustibles, and affect metal like the chill metal spell. Some affected metal will crumble to dust. When slain they explode in a ball of negative energy. Finally, if they ever come in contact with their opposite, the xeg-ya, both creatures will rush together and explode in a frozen ball of fire.