Oracle

Oracles are a Vex unit found in the Vault of Glass. Unlike normal enemies, they do not attack directly, but they are still very dangerous.

There appears to be two types of Oracles; yellow, which appear during the fight with the Templar, and red, which appear during the fight with Atheon. The yellow oracles cast a debuff called "Mark of Negation", which they cast on the entire party unless they are killed quickly. The debuff will kill anyone who still possess it when the Templar casts "Ritual of Negation." The red oracles will simply kill the party outright if not destroyed in time. However, killing them all will grant the fireteam a buff called "Time's Vengeance", doing bonus damage against Atheon.