Temporal Manipulation

While travelling backwards in time has been firmly established by modern science to be impossible, the passage of time in a region can be slowed or sped up by sufficiently advanced civilizations. So too is travel into the future, though the power requirements are prohibitive.

Utility

Temporal manipulation on its own is already able to freeze entities in eternity and abbreviate clone maturation times, but it is most impressive when used to augment other technologies. A fusion reactor or a Penrose sphere can have their power output vastly increased, whereas time being slowed down can serve as an additional layer in a ship's defense grid.

Access & Availability

Manipulation of the space-time continuum requires an extremely thorough understanding of universal mechanics, and actually making use of temporal manipulation on a macro scale requires equally robust power sources. Typically, only intergalactic civilizations are capable of doing so.