While finding ways to increase your maximum health is one of your goals in Elden Ring, you will also need to find ways to heal in all types of situations. Urgent Heal is the name of an incarnation that instantly restores your health points in the Elden Ring, making it a must-have for any character.
Do note that Urgent Heal only heals for a small amount. This incantation is supposed to be only used to escape death. It is not meant to bring yourself back to full health.
Urgent Heal Location in Elden Ring

Urgent Heal incantation in the Elden Ring can be acquired in two ways. The best and easiest method is to start the game as the Confessor Class. It is a starting spell for this class.

However, if you choose another class character, you will then need to buy the Urgent Heal incantation from Brother Corhyn at the Roundtable Hold for 1,000 runes. To reach the Roundtable Hold, progress the story until you reach Margit, the Fell Omen. At this point, Melina will take you to the hold, where you can find Corhyn standing next to the table.
If you fail to buy Urgent Heal the first time, then you will have to go to the north of the Altus Highway site of grace on the Altus Plateau. Corhyn will be present there and will sell you the Urgent Heal incantation.
Urgent Heal Uses and Stats in Elden Ring

Urgent Heal incantation in Elden Ring requires 8 Faith and 16 FP to cast. It also needs one spell slot and a good sacred seal.
The best part about Urgent Heal is that it can be used while in motion. So you can dodge and roll away from enemy attacks and use Urgent Heal to restore your health. This incantation heals you for 1.15 x Faith Incantation Scaling, which is a very small yet crucial amount to survive dangerous encounters.