Comic Title: Swamp Thing #20
Publisher: DC (National Periodical Publications, Inc.)
Address: 75 Rockefeller Plaza, New York, NY
Cover Date: Dec/Jan 1975
On Sale Date: September 9, 1975 Newsstand Date September 9, 1975
Source: Comic Reader, #122

Copyright Date September 9, 1975
Source: Library of Congress, Periodicals 1975

Frequency: Bi-monthly
Cover Price: $0.25
Page Count: 32
Editor: Joe Orlando

Title: "The Mirror Monster"
Pages: 18

Feature(s):
Swamp Thing (of Earth-1)

Writer: Gerry Conway
Artist: Nestor P. Redondo
Letterer: Marcos Pelayo
Colorist: Tatjana Wood

Reprinted In:
Swamp Thing:The Bronze Age Omnibus HC (2017)
Swamp Thing:The Bronze Age Vol. 2 TPB (2020)

Feature Character(s)

• Swamp Thing (last appearance in Swamp Thing #19; next appearance in Brave & the Bold #122)

Supporting Character(s)

• Matt Cable (last appearance in Swamp Thing #19; next appearance in Saga of Swamp Thing #17)
• Abigail Arcane (last appearance in Swamp Thing #19; next appearance in Saga of Swamp Thing #16)
• Jefferson Bolt (first name revealed; last appearance in Swamp Thing #19; no further appearances)

Villain(s)

• Ho'Tah Makanaw (dies in this story; last appearance in Swamp Thing #19; no further appearances)
• A second mindless Swamp Thing (last appearance in Swamp Thing #19; no further appearances)
• Earl Hobart and his followers (last appearance in Swamp Thing #19; no further appearances)

Other Character(s)

• Burton Sloan and Junior Sloan (last appearance in Swamp Thing #19; no further appearances)
• Frank Halston and a team of excavators (Carmody named; last appearance in Swamp Thing #19; no further appearances)

Comments:
The editor's note on page 7 inaccurately claims that Swamp Thing lost an arm in Swamp Thing #3. He actually lost the arm in Swamp Thing #5.

Another editor's note on page 8 claims that the engineers were attacked by a duplicate Swamp Thing. As shown in Swamp Thing #19, it was the real Swamp Thing involved in the attack.

Bolt refers to Alec Holland's bio-restorative formula as a super-soldier formula in this story.

This story is continued from Swamp Thing #19.

Synopsis:
Near the town of Gatorberg, an excavation crew triggers an explosion which destroys the Grotto of Eternal Youth which has kept Ho'Tah Makanaw alive for more than one hundred years. Angered at the destruction, Makanaw sends his Swamp Thing duplicate on a rampage. It attacks the construction crew and Matt Cable, who believes it to be the real Swamp Thing.

As the creature is drawn away from human eyes, it encounters the original Swamp Thing. A fight ensues. Meanwhile, Makanaw has gone into town seeking vengeance on the white man. He is confronted by Burton Sloan and killed during a fight. The duplicate Swamp Thing senses Makanaw and comes to his aid too late. The construction crew then uses explosives to destroy the duplicate. Everyone assumes that this was the original Swamp Thing, and that he is now dead. However, the real Swamp Thing returns to the swamps.