The X-Men (vol. 1) #40 (Jan. 1968):
“The Mark of the Monster!”
by Roy Thomas, Don Heck, George Tuska

The X-Men (vol. 1) #40

Title: “The Mark of the Monster!”

Medium: comic

Cover date: Jan. 1968

Publisher: Marvel
Written by: Roy Thomas
Art by: Don Heck, George Tuska

24 characters in this story:

(Click links for info about character
and his/her religious practice, affiliation, etc.)
Pub. #
Cyclops Cyclops (Scott Summers) hero
CBR Scale: SCBR Scale: I Protestant; mutant supremacist
Brotherhood of Mutant Supremacy; Summers Rebellion...  Marvel 8,371
The Beast The Beast (Hank McCoy) hero scientist
CBR Scale: ICBR Scale: S Episcopalian; agnostic
Academy of Tomorrow; Brotherhood of Mutants...  Marvel 5,233
Phoenix Marvel Girl (Jean Grey) hero
CBR Scale: I Episcopalian
Metro College; The Twelve...  Marvel 1,905
Iceman Iceman (Bobby Drake) hero
CBR Scale: I Jewish Catholic
Secret Defenders; Spider-Man and His Amazing Friends...  Marvel 1,752
Angel Angel (Warren Worthington III) hero
CBR Scale: I Episcopalian
Academy of Tomorrow; Horsemen of Apocalypse...  Marvel 1,741
Frankenstein's Monster (Robot) Frankenstein's Monster (Robot) villain
CBR Scale: D N.A.
[created by an alien race as ambassador, but went berzerk] Marvel 1
Changeling Professor X (Kevin Sydney) hero
  Factor Three; X-Men Marvel 23
Xavier Institute Xavier School for Gifted Youngsters supporting character group
  [high school] Marvel 373
Cerebro Cerebro
CBR Scale: I N.A.
[Xavier's mutant-finding machine, given sentience by Bastion] Marvel 9
X-Men X-Men hero group
  [1st app: The X-Men (vol. 1) #1 (Sep. 1963)] Marvel 9,958
unnamed museum staff unnamed museum staff supporting character group
  [saw Warlock's body return to crypt in museum] Marvel 1
Dr. Powell Dr. Powell supporting character scientist
  [led Arctic expedition that found Frankenstein robot] Marvel 1
scientists scientists
supporting character group scientist real/historical person
  [occupation] Marvel 1
The Museum of the City of New York The Museum of the City of New York
supporting character group real/historical person
  [museum] Marvel 2
unnamed curator unnamed curator supporting character
  [curator] Marvel 1
unnamed guard unnamed guard supporting character
  [couldn't stop X-Men going to Frankenstein robot in Museum] Marvel 1
unnamed freighter captain supporting character
  [Frankenstein's Monster Android stowed away on his ship] Marvel 1
unnamed alien race unnamed alien race
supporting character group
CBR Scale: D alien
[sent Frankenstein's Monster robot to Earth as ambassador] Marvel 1
Frankenstein's Monster Frankenstein's Monster
  First Line; S.H.A.D.E.... 
[Uses name Frankenstein in tribute to his creator.]
Marvel DC 990
(talked to, but not seen or
supporting character group real/historical person
  [police department] Marvel DC 1,396
Professor X Professor X (Charles Xavier)
(someone disguised or dressed as) 
hero scientist
CBR Scale: S religious
Brotherhood of Mutants; Genoshan Excalibur...  Marvel 4,999
Victor Frankenstein Victor Frankenstein
supporting character
CBR Scale: S Lutheran
[creator of the Frankenstein Monster] Lackington, Hughes, Harding, Mavor & Jones 156
Dorothy Gale Dorothy Gale
lead character
CBR Scale: I Protestant
[farmer; student] George M. Hill Company; Arrow, etc. 270
Mary Shelley Mary Shelley
supporting character real/historical person
  [wrote "Frankenstein"] Universal Studios 39

Reprints of this comic:
X-Men (vol. 1) #88 (June 1974): "The Mark of the Monster!"