King Sombra to himself:
No! My Cryssstaaalllsss....
The wave of pure happiness washed over him. Much like the ponies below, his flesh turned to living gemstone too. But the dark magic within his body that kept him alive reacted poorly, rapidly decaying and building up pressure within him. His body cracked.
When the second wave of magic came, he shattered into dust.
And below, the smiling form of Princess Cadance never realized that she had one more murder on her soul.