Resources

Reservation

Reservation sets aside life or mana for an ongoing effect, leaving that portion unavailable until the effect ends.

Rules at a glance

Reservation is not an upfront skill cost; the reserved resource remains unavailable while the effect is active.
Reservation efficiency reduces the portion reserved and has diminishing returns because it divides the base reservation.
Cost and Reservation Multipliers on supports apply to supported skills before the rest of the setup is evaluated.
Flat and percentage reservation are separate values; check the gem’s current level table.

Game-client explanation

Reserved mana can't be used or recovered until whatever is reserving it is disabled, so consider whether you will be able to use your skills with the mana you have remaining. Things that change how skills interact with your mana (like 'Blood Magic') also apply to mana reservation.

Heralds also reserve mana and grant benefits that are similar to some of the aura skills, however they only affect you. Heralds also have special behaviours that interact with ailments.

Some auras don't reserve mana or don't persist indefinitely. This is true of Vaal versions of auras such as Vaal Grace.

Vaal auras have a limited duration but grant very powerful bonuses for the short time they are active.