An Estus flask is first granted to the player by Oscar before he succumbs to death. Alternately, the player automatically receives the Estus Flask if they kill Oscar. Thereafter, players receive up to 5 Estus charges by resting at an unkindled bonfire. A kindled bonfire yields 10 charges; further kindling bonfires through Rite of Kindling rewards an additional 5 charges per kindle to up to 20 in total. Additionally, if the bonfire last rested at is kindled by another player, the player receives an extra Estus charge, unless the player is at 20 Estus, which is the maximum amount possible.
Estus Flasks are the basic healing items in Dark Souls. They are replenished via resting at bonfires. The amount they heal can be upgraded by offering Fire Keeper Souls to other Fire Keepers. The maximum amount of times an Estus flask can be upgraded is seven times. Only seven fire keeper souls can be obtained in one game. Four of these can be found scattered throughout the world, but the other three must be obtained by killing the firekeepers to claim their souls (or in the case of Anastacia of Astora, obtaining her soul from Lautrec after he kills her).
|Estus Flask Level||+0||+1||+2||+3||+4||+5||+6||+7|
Firekeeper souls are very rare (only 7 can be found per playthrough, and three are held by NPCs that the player may not want to kill or let die) and, though they can be consumed for humanity, they are usually better spent upgrading estus flasks. Upgrading estus flasks dramatically improves the player's ability to heal him or herself. For example, a player with twenty +7 Estus Flasks can heal up to 10,000 more HP in total than a player with twenty non-upgraded Flasks.
Phantoms of all types cannot rely on estus flasks for healing. However, they can still rely on all other healing items and spells, such as the Heal miracle, consuming solid humanity, etc. Friendly phantoms (not including NPC) are healed by estus whenever their host player uses one.
Players hit by a Lloyd's Talisman will not be able to drink estus for a limited duration.
Estus are fondly treasured by the undead. Oscar names it "an undead favorite". On the other hand, the living are not cordial about Estus. The undead hunter Lloyd created Lloyd's Talismans to aid in his extermination of the undead; Lloyd's Talismans block the healing ability of estus.