| Unofficial Challengers of the Unknown Index |
Credits:
| Story | France Herron |
| Art | Bob Brown |
| Lettering | Stan Starkman |
| Editing | Murray Boltinoff |
Feature Character(s):
Other Character(s):
- Monstro (first appearance; an embryo shot into the earth in 1900 which hatches in 1965, boring into the molten magma to mature and menace the earth in 2265)
Location(s):
- Challengers Mountain (in today and 2265 AD of an alternate future)
Credits:
| Story | Bill Finger |
| Art | Bob Brown |
| Lettering | Stan Starkman |
| Editing | Murray Boltinoff |
Feature Character(s):
Villain(s):
- Five unnamed scientists (first appearance for all; mutated by experimental radiation; begin stealing artifacts that are the last of its kind; all die)
Comment(s):
- The four receive new uniforms, sleeveless yellow form-fitting uniforms with red trim and an hourglass chest symbol.