S05E12: Descent
The origin of Mr. Sinister is revealed.
Previous Episode 
Season 1
Night of the Sentinels (1)
S1E1 / 31 Oct 1992
Night of the Sentinels (2)
S1E2 / 07 Nov 1992
Enter Magneto
S1E3 / 27 Nov 1992
Deadly Reunions
S1E4 / 23 Jan 1993
Captive Hearts
S1E5 / 30 Jan 1993
Cold Vengeance
S1E6 / 06 Feb 1993
Slave Island
S1E7 / 13 Feb 1993
The Unstoppable Juggernaut
S1E8 / 20 Feb 1993
The Cure
S1E9 / 27 Feb 1993
Come the Apocalypse
S1E10 / 06 Mar 1993
Days of Future Past (1)
S1E11 / 13 Mar 1993
Days of Future Past (2)
S1E12 / 20 Mar 1993
The Final Decision
S1E13 / 27 Mar 1993
Season 2
Till Death Do Us Part (1)
S2E1 / 23 Oct 1993
Till Death Do Us Part (2)
S2E2 / 30 Oct 1993
Whatever It Takes
S2E3 / 06 Nov 1993
Red Dawn
S2E4 / 13 Nov 1993
Repo Man
S2E5 / 20 Nov 1993
X-Ternally Yours
S2E6 / 04 Dec 1993
Time Fugitives (1)
S2E7 / 11 Dec 1993
Time Fugitives (2)
S2E8 / 18 Dec 1993
A Rogue's Tale
S2E9 / 08 Jan 1994
Beauty & the Beast
S2E10 / 15 Jan 1994
Mojovision
S2E11 / 05 Feb 1994
Reunion (1)
S2E12 / 12 Feb 1994
Reunion (2)
S2E13 / 19 Feb 1994
Season 3
Out of the Past (1)
S3E1 / 29 Jul 1994
Out of the Past (2)
S3E2 / 05 Aug 1994
The Phoenix Saga: Sacrifice (1)
S3E3 / 05 Sep 1994
The Phoenix Saga: The Dark Shroud (2)
S3E4 / 06 Sep 1994
The Phoenix Saga: Cry of the Banshee (3)
S3E5 / 07 Sep 1994
The Phoenix Saga: The Starjammers (4)
S3E6 / 08 Sep 1994
The Phoenix Saga: Child of Light (5)
S3E7 / 09 Sep 1994
Savage Land, Strange Heart (1)
S3E8 / 10 Sep 1994
Savage Land, Strange Heart (2)
S3E9 / 17 Sep 1994
Obsession
S3E10 / 24 Sep 1994
The Dark Phoenix: Dazzled (1)
S3E11 / 12 Nov 1994
The Dark Phoenix: The Inner Circle (2)
S3E12 / 12 Nov 1994
The Dark Phoenix: The Dark Phoenix (3)
S3E13 / 19 Nov 1994
The Dark Phoenix: The Fate of the Phoenix (4)
S3E14 / 26 Nov 1994
Cold Comfort
S3E15 / 04 Feb 1995
Orphan's End
S3E16 / 25 Feb 1995
The Juggernaut Returns
S3E17 / 06 May 1995
Nightcrawler
S3E18 / 13 May 1995
Weapon X, Lies, and Video Tape
S3E19 / 11 Jun 1995
Season 4
One Man's Worth (1)
S4E1 / 09 Sep 1995
One Man's Worth (2)
S4E2 / 16 Sep 1995
Courage
S4E3 / 23 Sep 1995
Proteus (1)
S4E4 / 30 Sep 1995
Proteus (2)
S4E5 / 07 Oct 1995
Sanctuary (1)
S4E6 / 21 Oct 1995
Sanctuary (2)
S4E7 / 28 Oct 1995
Beyond Good and Evil (1)
S4E8 / 04 Nov 1995
Beyond Good and Evil (2)
S4E9 / 11 Nov 1995
Beyond Good and Evil (3)
S4E10 / 18 Nov 1995
Beyond Good and Evil (4)
S4E11 / 25 Nov 1995
Have Yourself a Morlock Little X-Mas
S4E12 / 23 Dec 1995
The Lotus and the Steel
S4E13 / 03 Feb 1996
Love in Vain
S4E14 / 10 Feb 1996
Secrets, Not Long Buried
S4E15 / 17 Feb 1996
Xavier Remembers
S4E16 / 27 Apr 1996
Family Ties
S4E17 / 04 May 1996
Season 5
The Phalanx Covenant (1)
S5E1 / 07 Sep 1996
The Phalanx Covenant (2)
S5E2 / 07 Sep 1996
A Deal with the Devil
S5E3 / 14 Sep 1996
No Mutant Is an Island
S5E4 / 21 Sep 1996
Longshot
S5E5 / 05 Oct 1996
Bloodlines
S5E6 / 26 Oct 1996
Storm Front (1)
S5E7 / 02 Nov 1996
Storm Front (2)
S5E8 / 09 Nov 1996
Jubilee's Fairytale Theatre
S5E9 / 16 Nov 1996
The Fifth Horseman
S5E10 / 08 Feb 1997
Old Soldiers
S5E11 / 22 Feb 1997
Descent
S5E12 / 06 Sep 1997
Hidden Agendas
S5E13 / 13 Sep 1997
Graduation Day
S5E14 / 20 Sep 1997
Cedric Smith
Professor X (voice)
Norm Spencer
Cyclops (voice)
Catherine Disher
Jean Grey (voice)
Alison Sealy-Smith
Storm (voice)
Lenore Zann
Rogue (voice)
Cal Dodd
Wolverine (voice)
Alyson Court
Jubilee (voice)
