The soft, morning glow of sunrise filters in through the chamber of Starswirl the Bearded. The stallion himself remains steadfastly asleep. That is, until a quiet thud outside the door disturbs his slumber.
"By Faust, what is that so early in this morning?" Starswirl yawns, rubbing an eye. His attention drifts to the snow-covered landscape outside the window. "My, there must have been a blizzard last night."
He sits up, brushing loose straw from his face. "Well, I suppose there's no harm done in answering the door at such an early hour. I certainly do hope this commotion hasn't disturbed the children."
Starswirl walks to the door, his head held in a curious tilt. Slowly, he opens it and peers outside. All around, there is nothing but a blanket of white. However, a curious set of tiny hoofsteps appears to have trudged through the snow, all the way... to this very doorstep.
"By Faust." The stallion repeats, his eyes landing on the collapsed form of a shivering filly. "Where are your parents? Do you not have a caretaker?" He sticks his head further out the door. There is nopony else to be seen. He returns his attention to the filly. "Very well then. I shall be your caretaker for now. No foal should be shivering on this frigid day."
"So you claim to have been orphaned as of the previous week."
The filly nods. The young Celestia and Luna watch on in curiosity, though neither are at the age to speak as of yet.
"These are Celestia and Luna. They are the only two Alicorns known to exist, and as such have been deemed royalty. You will be their elder sister and playmate."
"Elder... sis--" the filly breaks out in a coughing fit before she can finish her sentence. Her stomach grumbles in response to the disturbance.
"Tsk, Starswirl, you must one day learn your limits!" Starswirl lectures himself. "The two fillies you've adopted have already eaten you out of what little food you have, and now you take on a third?"
He glances at the filly again.
"I do not eat very much, sir." The filly responds, leaning forward a little. "I have gotten by on roots and snowmelt for days."
"Unacceptable!" Starswirl booms, surprising all three foals in the room. "Little filly, do you have a name?"
The filly shakes her head. "I have been called many things, but I do not have a singular given name, sir. I am as free as the ravens that soar overhead, and yet I lack a true identity."
"Raven." Starswirl strokes his beard. "Raven is a good name for a pony such as you. Ravens are intelligent creatures. Do you know how to read and write?"
Raven nods.
"Then you shall henceforth be known as Raven Inkwell," Starswirl declares. "Raven Inkwell, third daughter of the mage Starswirl, elder sister and protector of the Alicorn Princesses Celestia and Luna."
"...Protector?"
"Elder siblings are often tasked with the protection of the younger. I myself once was nurtured by an elder sibling, but he has long-since passed on."
Raven looks past Starswirl to the two Alicorns behind him. Celestia babbles some nonsense to Luna. "You can't possibly task me with the oversight of nigh-immortal beings, sir. We are but mortals in the presence of demigoddesses."
"Demigodesses, who, as of now, are still too young to speak." Starswirl corrects.
"That does not resolve the issue of our own mortality in comparison to theirs."
"Such complex speech at such a young age!" The stallion remarks, "I may not be able to use it on myself, but I do know of a spell that can somewhat resolve the predicament of mortality."
"You... can make ponies immortal?"
"Not immortal per se, more a bonding to one that outlives the other. You will continue to grow, age, and eventually die, but your soul will live on, materializing in new bodies as seen fit by the machinations of the bond itself."
"You say bodies as in there may be plural."
"Unfortunately, this is indeed the case. There is no way for the bonding spell to ensure that only a single vessel is fabricated upon your death. There may be none, leaving you to wander as an abandoned soul, or there may be hundreds, each with a copy of your original soul to inhabit their bodies."
Raven furrows her brows. "But why me? It has been hardly a day, yet you offer me the chance to enjoy not only a life forever associated with two demigoddesses, but a life that will last as long as they themselves may live. You say that the only price I will pay for this eternal gift is to defend these sisters as if they are of my own bloodline. I do not understand your methods, sir."
"I do not understand my methods either. I do not expect to ever fully understand them. Perhaps it is fate that you appeared on my doorstep, famished and weak. Perhaps it is pity. I do not know. And yes, that is my lone request. Please, if you allow me to bestow upon you the powers of the bonding spell, defend little Celestia and Luna as if they are your own sisters."
"I will refer to them by title. I do not yet feel comfortable fully associating myself with such power. Such disassociation may also serve to better insulate myself in case if I or any of my descendants are compromised." Raven pauses as her stomach grumbles again. "I also desire proper sustenance, now that I no longer live in the wilds."
Starswirl gives a nod. "Thank you, Raven Inkwell. Until you are ready for the spell, I will raise you alongside the sisters as my own."
Raven raises a hoof. "One more request, if you please."
"Yes?"
"I am unable to see very far. Is there any remedy for my ailing eyesight that you are aware of?"