Regeneration crisis was a possible symptom of regeneration. Metamorphic symbiosis regenerators were used in cases of acute regenerative crisis. (TV: Mawdryn Undead [+]Loading...["Mawdryn Undead (TV story)"])
After having some of his regeneration energy siphoned into a newly regenerated future incarnation, who he had learnt had fallen asleep, the Third Doctor suggested that he was suffering from a regeneration crisis. (PROSE: The Christmas Inversion [+]Loading...["The Christmas Inversion (short story)"])
Following the Fourth Doctor's regeneration, the Tremas Master made a failed attempt to defeat the Fifth Doctor during his regeneration crisis. (PROSE: The Quantum Archangel [+]Loading...["The Quantum Archangel (novel)"], TV: Castrovalva [+]Loading...["Castrovalva (TV story)"])