So,  
Because probably no one will understand this, and its probably not the greatest head canon ever, I just thought it was an interesting idea so PLEASE dont hassle me about this drawing not making any sense
 
But basically what this is, its like… when Trixie finally got the power she wanted, being an alicorn, she goes mad with power. Insane.  
And the way celestia deals with things like this is just get rid of it, so this is Trixie slowly being turned to stone by Princess Celestia.  
Yeah.  
its kinda silly but this was an old drawing i made 6 months ago, so I just wanted to redraw it.