The Last Survivor DLC for Alien Isolation is currently a freebie at Epic Games Store. This is a new addition: it was not yet free yesterday when the base game was given away. To claim it, you need to claim the base game again: this will add the DLC to your account. Link: https://www.epicgames.com/store/en-US/p/alien-isolation
After you have claimed the game, you can check that you own it on the DLC page (it should say "Owned"): https://www.epicgames.com/store/en-US/p/alien-isolation--last-survivor
From the DLC description: " As Ellen Ripley, it is down to you to complete the last mission on board the Nostromo. The rest of the crew are dead. In a desperate bid to survive you must set the ship’s self-destruct and attempt to reach the escape shuttle. "
