10 Longest Gaps Between Doctor Who Character Appearances
8. The Sisterhood Of Karn (13,810 Days)
Steven Moffat was the king of the deep-cut Doctor Who reference, and so it was that the Sisterhood of Karn became recurring characters between 2013 and 2015.
Originally appearing in 1976's The Brain of Morbius, the Sisterhood were the keepers of the sacred flame, which created the much sought-after Elixir of Life. The Fourth Doctor found time during his busy schedule battling the resurrected Time Lord villain Morbius to reignite the flagging sacred flame.
37 years later (our time), the Eighth Doctor was in serious need of the sacred flame's healing properties in 2013's The Night of the Doctor, and it was the Elixir of Life that triggered his eventual regeneration into the War Doctor.
Sisterhood member Ohila would later arrive on Gallifrey in the Series 9 finale Hell Bent, to chastise the Twelfth Doctor for his reckless behaviour. To this day, this is the last time the Sisterhood has been seen in a televised story.