The Warding Altar, or "Warding Altar of Trefalgar", is a powerful artifact that guards Frostfire's lair. Once you destroy it, you gain access to Frostfire's inner sanctum. It can be found on the Take Out Frostfire mission from Flux. (Levels 5-15)
Also, two virtually identical objects to this one can be found during the mission Investigate the lost city of Oranbega from Miriam Bloechl or Laura Brunetti (Levels 25 - 29). Those will have to be destroyed as well as they are mission objectives.
This object seems to be regenerating the health of the villains around it.