What is the name of the main healing item in Dark Souls?

Explanation

In Dark Souls, the Estus Flask is the primary healing item that can be used to restore health when it reaches critical levels. It's an ancient, legendary flask said to be blessed by the goddess Estus herself. The player starts the game with only one full flask, but can find more along their journey. When used, each sip restores half of the player's total HP. However, each use also depletes the fluid inside the flask, and once empty, it cannot be refilled until the player rests at a bonfire (checkpoint). Therefore, proper management of the Estus Flask becomes a crucial aspect of survival in this unforgiving RPG.