Lucidstuck has a revival system in case Derrick or Alice get killed within the dream world. Marshmallows have been explained to revive Derrick or Alice if he/she eats them while in a blackout dream induced specifically from death. Upon eating the marshmallow, they will instantly escape from their blackout dream with plenty of time to return to their body before anything else does.
Marshmallows are exclusive to Alice and Derrick. Derrick or Alice will not encounter another marshmallow if they already have one. Reviving in general has not been introduced yet as a skill that the dreamers can use.