Chapter 1
Princess Celestia was used to having Twilight Sparkle barge in on her. In the throne room; in the solarium; painfully frequently in the bedroom; and more than a few times into the bath. The frequency had decreased once Twilight moved to Ponyville - and increased back now that Twilight had recently become an alicorn and discovered long-distance teleportation - but the fact that any moment in her life could be abruptly interrupted by a purple mare appearing with (in her mind) pressing questions was just something Celestia had learned to live with.
This, however, did not mean that those around her were as prepared for it.
Air displaced with a soft thump of magenta magic as Twilight popped into existence. "Princess Celestia, I need to talk--"
Her question was preempted by horrified screaming from the other dignitaries present - as an alicorn suddenly appearing in the middle of a sauna was distinctly unexpected - and by Twilight's own shriek - as she had teleported herself atop a pile of steaming hot coals.
Princess Celestia placidly waited for the chaos to sort itself out and tried very hard not to laugh.
Twenty minutes later, they were out of the new sauna the yak ambassador had been showing off and the crowd had calmed down. Princess Celestia guided Twilight through the hall to a more private place - her study.
Inside and over tea, the elder Princess gave her student a small nod. "You were saying?"
Twilight Sparkle stopped fidgeting with the bandage on her burnt hoof and finally remembered why she was there. "Oh! Um, I did have a question about, um..." Twilight shifted uneasily in her chair. "Why are all alicorns mares?"
Princess Celestia sipped her tea to buy a few more moments before confronting the question. "The answer is that not all alicorns are. Or were, more accurately."
She paused to sip again, letting Twilight hang waiting. It was something Celestia had found added some enjoyment to these conversations - having her student enraptured never ceased to give the Princess a boost of pride.
"Once long ago, there were alicorns of both genders. But we were very few in number. Tell me, my student. Since you have ascended, what has been the greatest problem you've had?"
Twilight considered for just a moment. "The fact that ponies keep trying to take pictures all the time and I've caught three different tabloid reporters in my bathroom?"
There was a pause as Celestia used centuries of experience at controlling her emotions to keep from snorting tea through her nose. "A valid complaint, Twilight, but not what I meant. As an alicorn, we have the magic of all three tribes within us and in many ways each aspect is stronger than an individual of any one would be. That power comes at a cost to our metabolism - I'm sure you've observed an increase to your appetite."
With a little laugh-snort, Twilight rolled her eyes. "Well, Spike certainly has noticed it!" She cleared her throat, trying to become serious once more. "I mean, yes Princess Celestia, I have noticed it."
"Maintaining an alicorn's body requires considerably greater energy than any other pony's. And when we enter a state where our bodies need even more..." Celestia paused, waiting to see if Twilight would fill in the gap. She didn't - she simply continued to hang on Princess Celestia's every word. "Pregnancy. I mean during pregnancy, Twilight. An alicorn's body requires far more than what normal sustenance can provide."
Understanding twinkled in Twilight's eyes. "Oh, I see! So that explains why alicorns never overtook the other tribes in terms of numbers despite their strength and longevity! A slower breeding cycle would--"
The elder Princess cleared her throat. "Actually Twilight, that's only part of the story. You see, in order to gain the energy needed to survive and birth a healthy foal, alicorns had to.." Celestia trailed off for a moment, putting off the information for just a few seconds. But it was inevitable from the moment Twilight asked the question. So she closed her eyes and bit the bullet. "Consume their mates."
".....I'm sorry, could you repeat that?"
"It was the norm for a female alicorn to kill and consume their mate after fertilization. The more nutrient and magically rich food source would create enough of a buffer to allow the alicorn to survive pregnancy and foster the foal's development." Celestia still couldn't bring herself to look at her student.
"So you--"
"Ate the males of our species into non-existence," Celestia confirmed.
Twilight started giggling. Not the cheerful laughter of Pinkie Pie, nor the devilish chuckle of a prank-playing Rainbow Dash, nor even the nervous titter of Rarity as she tried to explain why her latest creation looked like a neon nightmare. No, Twilight's giggles were distinctly and thoroughly unhinged. "Sexual cannibalism," she snuck out between laughs. "Alicorns engage in--" She devolved into deranged laughter mid-sentence.
A quiet sigh slipped from Celestia's lips. "And this is why I was reluctant to tell you, Twilight."
"No! No, it's fine." A small twitch developed in Twilight's left eye. "I'm totally fine with the revelation that Princess Celestia has probably almost certainly definitely murdered and eaten dozens of ponies."
Celestia shook her head. "It isn't quite so bad, Twilight--"
"ISN'T QUITE SO BAD?!"
Wisps of golden magic covered the younger alicorn's mouth to silence her. "Isn't quite so bad as you think, Twilight," Celestia repeated. "First of all, there is a reason I haven't been romantically involved with anypony in centuries. Secondly, modern times have a much greater availability of food than in pre-Equestrian times. And there's also the fact that the alicorns of today have replaced that need with external sources of power. By being tied to the Sun and the Moon, such extreme actions are no longer needed. We can simply pull the power from other sources."
"So you mean that--" Twilight's question was cut off by her own understanding. "My brother!" Her jaw dropped. "But Shining Armor's-- I mean he's-- Cadance didn't--"
Gently, Celestia raised a hoof to silence Twilight. "Her connection to the Crystal Heart overcame any physical need and may have even played a role in Flurry Heart's development into what she is. And as well, Cadence chose to deviate from tradition. I suspect that she couldn't bear what the loss of Shining Armor would do to you, Twilight."
Twilight breathed a heavy sigh of relief at that. "That's good to know. I was worried that maybe for their next foal she... wait." Her eyes narrowed. "You said something about tradition?"
"Indeed, Twilight." Celestia paused to sip her tea. "While such acts are no longer needed physically, it is still customary for alicorns to do so. Tradition is a powerful thing, after all."
There was a long, ironically pregnant pause before Twilight hesitantly asked her next question. "Princess Celestia? If... if alicorns consume their mates afterwards, does, um... does that mean I have to eat Rarity?"