Amaranth

Amaranth was a device of Gallifreyan design created by the Time Lords.

It was capable of of warping reality in the nearest space and was influenced by the most rational potential. This means that they look for parts of the universe that have become unstable in some way and rebuild them along more rational line.

The first amaranth was created by maintenance engineers on Gallifrey to help counteract the warping effects caused by the black hole on the space time continuum. The Doctor possessed one such device which contained an emergency function which was to transport its user to a more stable part of space. (NA: Christmas on a Rational Planet)