In the Outer Worlds you will be travelling with A.I. companions if you want some help on your journey. These companions have special abilities and can help you in a fight, but they can also be killed in action and depending on which game difficulty you are playing on they can be revived.
Use the Inhaler to Revive Companions.
If you’re playing one of three standard difficulty modes, you can revive your companions mid-fight if you have a specific perk unlocked. In Tier 3 if you purchase the “Don’t Go Dyin’ on Me!” perk when you use the inhaler during battle any downed companions are revived with a small amount of health. Only downside is that the cooldown is 15 minutes.
Equip Companion Perks
Companions also have perks that can be equipped and one of them is that they will revive themself. The Second Wind perk for companions will allow them to heal partial health and continue fighting when downed.
Companions can die permanently in Supernova
If you’re playing on Supernova difficulty things are a little bit trickier. Companions can permanently die in Supernova mode. Your best bet is try and revert to an early save to get the companion back in this game mode.