Last Breath (5e Feat)
From D&D Wiki
Your determination and physical resolve grants you the ability to hold on just a little longer. You gain the following benefits:
- Increase your Constitution score by 1, to a maximum of 20.
- When you are reduced to 0 hit points but not killed outright, you can drop to 1 hit point instead. You can't use this feature again until you finish a short or long rest.