Season Eight: The Last Journey
(80-85: Six Degrees of Progressive Darkness)
Episode Eighty: Sunshine (Can You Feel It?)
Episode Eighty-One: Cloud Mountain (The Last Adventure)
Episode Eighty-Two: Polar Eclipse (Bare Me the Details)
Episode Eighty-Three: Can't See (C Flat)
Episode Eighty-Four: Pitch-Perfect Dark (Jet Black)
Episode Eighty-Five: Final Times (Constant Darkness)
AFTER THE END
Episode Eighty-Eight: The Cold Bend of Empty Space Feasts Grey
Fun fact: This story arc, which started with Season Seven, took five years to do. You wouldn't believe how many eights and fives are contained in this ending.
Good luck understanding what the ending actually is!