As soon as Brightwing returned from her quiet night flight, she found the diary of Diamond Tiara along with a family photo album and started to study, to find out as much as possible about Diamond Tiara's friends and family as she possibly could. She remembered when she was back at school in the Hive...
Mr Opaque turned around and turned for a few seconds into a horrible thing with two legs and two hands, before regaining his normal changeling shape. Oh stallion, is he pissed! Brightwing thought. He only changes into that horrible shape when he's really angry. He glared at the class. "Yes, I was once a pupil too forty years ago, and I admit that I was not a perfect one, so I know how it is-but the next person I catch talking out of turn or throwing a paper plane in my class is going to get the cane across their backside. What I have to teach you will serve you well and give you a source of love for the rest of your lives. When you replace somebody, you need to at once find out as much about them as you can. Diaries for example are a prime source. The more you find out, the more you lessen the chance of being uncovered as a changeling, which would be a disaster for you. I put this into practise. My pony wife thinks that I spend two months a year working in the griffin kingdom whilst in fact I'm spending it teaching you lot. The other ten months of the year I spend teaching colts and fillies."
She finished looking at Diamond's diary and thought Some things are going to change.Dramatically. I don't want to be a spoilt snooty filly. I want to have as many friends as possible. before settling down in Diamond's luxurious bed. It was a bit different from the changeling hammock of changeling silk that she was used to, but she soon got used to it. The next day a servant woke her up and she went to school, careful to kiss her parents goodbye first and be kissed in return. She soon came across Silver Spoon being nasty as normal to the Cutie Mark Crusaders. "Blank flanks, you'll be blank flanks forever, or maybe you'll end up getting cutie marks for being annoying as that's all you'll ever be good at," Silver Spoon snapped.
"Silver, that's not very nice," Brightwing replied. "Remember the motto of our country, chosen by the Goddesses themselves... Friendship is Magic. Remember what Ponyism says...welcome new ponies to the Herd."
Silver stared at her as if she now had griffin claws instead of hooves. "Diamond, what's got into you? You're my best friend...are you turning into some sort of religious freak? You're scaring me now."
"Silver, I'm not a religious crazy and I value your friendship, I really do, but I want to have as many friends as possibly, even blank flanks, who are full of potential," she said, and turned to Apple Bloom, Scootaloo and Sweetie Belle who were as shocked as Silver Spoon at her being nice to them. Silver Spoon stuck her nose in the air and trotted away, horrified at what Diamond had said. During school Brightwing learned all the names of those in her class when the register was read out, and after school she went out to her new friends. "Would you like to come home and play chess with me? You might be able to become Cutie Mark chess players. Or if that idea bores you, why not join me in the family swimming pool?"
Later that evening, as the moon rose and they headed back home Sweetie Belle said to her friends "Don't you think something is wrong with Diamond Tiara?"
They shook their heads. "I see nothing wrong if she's stopped being such a brat," said Scootaloo. "With her helping us we'll soon get our cutie marks."
That evening Sweetie Belle looked at a recent birthday present that Rarity had given to her about the monsters of Equestria, and the article on Changelings caught her eye.
Changelings
The Changelings, in their original state look like a cross between a pony and an insect, with black pony-like bodies and green insectoid wings. Although their legs and wings appear to have holes in them, these holes are part of them and do them no harm, instead making it easier for them to change into almost any shape. Changelings are born as grubs and stay that way for a year, and in this state can only feed on love, without which they starve to death.
Adult changelings infiltrate areas, kidnap ponies, griffins and others and take their place, feeding on the love that relatives and romantic partners have for them. Whilst adult changelings can feed on other things then love, they need love to remain healthy in the long term. They are often sweeter then the ponies they replace as they want a source of love that they can feed upon for the rest of their lives.
The victims meanwhile have cocoons woven around them and are taken back to the hive where their love feeds the grubs. Changeling hives can be the size of Equestrian towns, and are well guarded. Non Changelings who get too close are seen by the sentries and tend to end up hanging in a cocoon within a feeding chamber, as Changelings see other races in their territory as a source of free love. To uncover a Changeling, shine a light spell through a cut diamond and the true shape of the changeling will be reflected in the diamond.
"So that's what happened to Diamond Tiara," Sweetie Belle said quietly to herself. "She's an imposter. Legally, I should let everypony know what has happened before other ponies end up getting replaced, but Diamond is most likely beyond rescue, and besides, I like the new Diamond much better then the snooty bratty filly that she was, who never said anything nice to us. I will tell my fellow Crusaders tomorrow and see what if anything they want to do about it."