This guide was created just to help those who don't know how to unlock the new survivor from 1.0 update.
The Most Simple Step
The only thing you have to do to unlock the Captain is to finish the game in any difficulty.
Okay, But How?
Simple, start a run like any other on any difficulty with any character. Upon reaching the fifth stage called ''Sky Meadow'' there will be a unique portal different from the conventional one. All you need to do is interact in the middle of the portal that will take you to the final boss and, after defeating him and finishing the game, the Captain will be unlocked.
In order to finish the game and unlock Captain, the Primordial Portal must have this configuration.