Taking part in battles will cause your Temtem to lose HP when they’re hit. If their health reaches 0, then they’ll be knocked out of the fight completely. When this happens, they don’t actually die, they just become inactive and unusable.
Even if you win the battle, any Temtem you have will not be revived, and will remain knocked out inside of your squad. You’ll need to bring them back to life yourself. If your entire squad is knocked out, then you’ll be sent back to a town and lose some currency.
You can read our quick guide below for reviving Temtem. For more Temtem Guides and Best-of lists on PC, PS4, Xbox One & Nintendo Switch, make sure to check out our dedicated area here!
Reviving Temtem
Temtem can be knocked out pretty easily during a battle. Especially if they are under-levelled or are countered element-wise. You can prevent them from being knocked out by switching out weaker Temtem, or by replenishing their health during a fight.

Now there are medical items you can use to restore your Temtem on the fly. However, a more cost efficient and faster way would be to use HealTem Stations.
These are objects you can interact with, found inside Temporiums. A Temporium is the main store that can be found in towns, and sells items such as TemCards and healing items.

The image above shows a few HealTem Stations inside the Temporium. Interact with one, and all of your 6 Temtem will be healed. Any that are knocked out will also be revived and set to full health, all for free. You can come back here whenever and as many times as you need.
With them being a bit out the way, it’s recommended to buy some Smoke Bombs from a Temporium so you can always teleport back.