The Oracle is an aerial Protoss support vessel devised for scouting and economic disruption.
A psionic warship, the Oracle was developed by the Protoss after the first phase of the Second Great War, in order to maximize the effectiveness of their war machine against their enemies.
Entomb: Area of effect spell. Encases minerals in a shell, making them unharvestable for ~1 minute. The shell can be destroyed on each mineral field.
Phase Shift: Phases out a unit for approximately 45 seconds, preventing it from being attacked, using abilities, researching, or building.
Pre-Ordain: Gives vision of a target building and what it is constructing or researching for 2 minutes. Gives vision of hatcheries, but does not show what larvae are evolving into.
In the game series, the Oracle is a concept idea for a new class of Protoss aerial support unit.
For more information see Oracle on the parent site.