The Challengers of the Fantastic are the Amalgam version of DC's Challengers of the Unknown and Marvel's Fantastic Four.
Reed 'Prof Richards' was a scientist who worked with Victor Von Doom. They created a rocket with cosmic shielding in an attempt to make space travel safe from cosmic mutations. Aboard during the test flight was Sue 'Ace' Storm of SHIELD and two civilians, Senator 'Rocky' Grimm and Sue's younger brother Johnny. Von Doom controlled the mission from Earth.
Von Doom grew jealous that Reed would get all the credit for something he helped with and sabotaged the flight. The rocket fell from orbit and crashed into Earth. All survived and they looked at this as a second chance at life. They joined together as the Challengers of the Fantastic to help human kind. Their symbol is an hour glass, the idea coming from when they joined hands to make the team official.
The Challengers of the Fantastic are based in Fantastic Mountain, just north of New York City. They have stopped such threats as Multi-Masters, Galactiac and of course, Doctor Doomsday.