Board Thread:Supergirl discussions/@comment-9346948-20181212011845/@comment-26618197-20181212191946

Well there's a couple options for what the deal was:

1) Oliver promised that they'd fight in the upcoming crisis. He had put his complete faith in Barry and Kara's ability to stop the crisis before making the deal so there's that.

2) Oliver offers his own life. Very likely but it won't stick because the event will probably be midseason and that would just be so depressing. It's possible that Oliver sacrifices himself then in the end when the worlds merge Oliver reappears with slightly altered memories