Regeneration energy

Regeneration energy was the energy a Time Lord produced as a product of regenerating. It was typically golden in appearance, (COMIC: The Forgotten, TV: The Parting of the Ways, The Stolen Earth, The End of Time, Day of the Moon, Let's Kill Hitler, The Night of the Doctor, The Day of the Doctor, The Time of the Doctor, Hell Bent, The Lie of the Land, World Enough and Time, The Doctor Falls) but it could occasionally be a bright white colour instead. (TV: Utopia)



The Tenth Doctor remarked that the energy was in excess for roughly 15 hours after regenerating, enabling him to restore his hand after it was chopped off. (TV: The Christmas Invasion) River Song was also able to survive being shot by a group of Nazi soldiers due to the excess energy. (TV: Let's Kill Hitler) It could also be harmlessly expelled through the mouth for a while after regenerating. (TV: The Christmas Invasion, The Eleventh Hour)

The energy itself was quite powerful, typically causing those nearby to back away, (TV: The Parting of the Ways, The Stolen Earth, Let's Kill Hitler, Day of the Moon) and once caused significant damage to the Tenth Doctor's TARDIS. (TV: The End of Time) It could also be used as a weapon, River using it to knock down several soldiers (TV: Let's Kill Hitler) and the Eleventh Doctor was able to destroy an entire Dalek fleet using said energy. (TV: The Time of the Doctor)



The energy was also capable of creating an entirely new individual based on the Time Lord who produced it. In one instance, the Tenth Doctor used up one of his cycle's regenerations while still keeping the same face by channelling it into his former hand which was sliced off by the leader of the Sycorax (TV: The Christmas Invasion), allowing himself to heal his body, yet avoid physical changes. This regeneration energy remained active and was accidentally interacted with by a human, Donna Noble, triggering a two-way human-Time Lord meta-crisis which caused the hand regenerate the missing body of its owner, creating a human-Time Lord copy of the Doctor and causing Donna gain the mind of a Time Lord. However, the presence of two minds inhabiting Donna at once nearly destroyed her and the Doctor was forced to block all memories of him from her consciousness to stop her Time Lord half from remaining active. (TV: Journey's End)

The energy could also be conjured for use without the need to regenerate. The Eleventh Doctor could willingly expend some of his remaining regeneration energy to heal River's broken wrist. (TV: The Angels Take Manhattan) The Twelfth Doctor could willingly expend regeneration energy to restore Davros' eyesight (TV: The Witch's Familiar) and fake a regeneration. (TV: The Lie of the Land) His Shadow World counterpart also used a device to siphon energy from his own future to temporarily restore his eyesight. (TV: Extremis) River Song used all of her remaining regeneration energy to bring the Eleventh Doctor back to life, the process nearly killing her. (TV: Let's Kill Hitler)