For Heroes:

On a mission into a Hydra base you and the team discovered a strange machine with a blue glowing center big enough to walk through. Steve hit a switch by accident making it suck you and (other canon character/s and or OC/s of your choice) into the blue swirl sending you back to the 1970's.

For Villains:

Hydra has been creating a time machine for a while. This is your chance to go back do anything kill anyone.

OC choices can be found on the my main characters chapter or additions scatter through some of the chapters