From the FAQ:
LP (Life Points) represent the amount of times your Merc can fall in battle before becoming exhausted. When a Merc falls in battle, it will lose an LP. When the merc’s LP reaches 0, it will “die” and will become unable to be deployed until resurrected for free or Stars. If Mercs are resurrected for free, there will be a delay before they are able to fight again. If Mercs are ressurected with Stars, they can be used again instantly. LP does not decrease when a Merc falls during a Boss Raid or an Arena battle.
A Mercenary loses 1 LP every time it dies in a battle. Reviving before the end of the battle does not negate the LP loss, so the only way to avoid LP loss is to avoid dying entirely.
If a Mercenary enters a stage with 1 LP and dies, it cannot be resurrected in-battle.
A fallen/dead Mercenary will still appear in your Mercenary list, but will not be usable until revived.
LP can be recovered in two ways:
- Free revive
- This can only be done when the Mercenary's LP has been completely depleted/fallen to 0
- Reviving a Mercenary will bring their LP back to max (example: 0/18 -> 18/18)
- The Mercenary will be revived after a certain amount of time
- The time it takes to revive a Mercenary is shown on the Rebirth window
- With stars
- This costs 5 stars to perform, but the merc will be revived back to max LP instantly.