A rip field is an effect produced by xel'naga technology that quickly disintegrates matter at a molecular level. They can be detected by the gravitational distortions they create. Fields mat warp time and space.
In StarCraft II: Wings of Liberty, rip fields are encountered in the mission, "Maw of the Void". They are generated by rip-field generators. Units unprotected by shields constantly take damage while within a field.
Rip fields continue to deal damage even when the "god mode" cheat is used.