“Hello children.”
 
Lets talk about sizes again, because i want to: Starburst is slightly smaller then most ponies, easily looking like a foal next to her cousin Flurry Heart (though as a pegasi - she has inherited her mothers “royal wings” to make up some for her short height.)  
Flurry is taller then the average pony even in her young age. (a normal pony head would he roughly right between the two)  
But they are both Dwarfed by the towering size of Nyx - Whom, as the clone of Luna’s super powered and super sized persona a la Nightmare Moon, experienced a growth spur that would give Gigantism a run for its money.
 
And with that size - combine with her intimidating heritage is enough to make even Giant-wing-Flurry Heart cower from sheer presence alone.
 
The other purpose with this image was to show Nyx as the polar opposite to the Royal rebels. She’s a well dressed, well mannered scholar with a chest decorated with medallions for many heroic acts in the service of Equestria.
 
The only thing that broke the image of perfection was the pair of glasses that sat halfway up her horn, attached by the faintest glimpse of magic. - It was a place where she would often forget her glasses.
 
Nyx was - and had always been - the model daughter of Twilight Sparkle.
 
And it infuriated Starburst. The little misbehaving, ragged, tomboy-ish rebel would not let herself be discouraged or intimidated by her elder sibling in any way. (in fact - being a folly to Nyx was very well what spurs Star on the most.)
 
She was also the one pony who could look up on the likes of Nyx and Flurry (if only because she was shorter) without the slightest awe, fear or reverence.
 
Even as Nyx levitated several heavy volumes using only the tip of her horn, the utmost minimum of her magical power, Star stared down Her bigger sister in defiance.
 
Nyx stared back as she leaned as casually as she could again a nearby lamppost.
 
The thing actually creaked and bent from the force.
 
“Now” She said “what have you two done this time?”
 
Note: This is probably the best picture of Nyx Ive ever made.And of starburst too. The difference between the two realy comes of strong.