>>724816952
Aight.
So the ideal estus is the one Oscar gives you. This is a "perfect" estus flask.
These don't exist anymore by DS2 or 3.
The flask isn't so much the limiting factor as much as the bonfire itself in terms of charges. Less kindled bonfires simply don't generate the same amount of heat.
The fire keeper souls "insulate" the flask. Not really against heat loss, because this isn't "real" heat, but against the loss of "soul" associated with the flame. Fire keepers themselves tend the bonfires, so their souls stabilize the essence carried within.
The estus shards of DS2 & 3 are literally repairing the estus to hold more, and return to the more intact estus of prior eras. The flame can no longer be kindled the same way, there's just not juice for it.
Undead bone shards/dust/whatever are bits of prior undead that linked the flame. Their souls are thus intrinsically tied to the bonfire, and makes the flask more "like" a bonfire. This achieves the same result of stabilization of the essence inside.
Ashen Estus is something else, and also provides insight into how Estus works, because Ashen Estus is explicitly stated to turn the heat of a bonfire cold.
As Ashen Ones are, on a fundamental level, different from the undead of DS1 & DS2, their Humanity has been stripped in a way "normal" undead aren't. Ashen Estus is, instead of refilling the essence of soul Estus normally does, refilling the "void", the "hollow-essence" that existed in primordial humanity, before the soul was thrust onto them.
