We all know the Crystal Heart works with the feelings of the crystal ponies. It's obvious he planned to use the Heart to collect love to give it all to his love, Queen Chrysalis.
As we all know (not really), they are the prince and princess of the love poison story. They used dark magic to make themselves immortal, so death could never set them apart. Now Chrysalis needs to feed on love, and so Sombra made the Crystal Heart to collect it.
I am really inspired right now. I cannot reveal my inspiration yet, so I'll just leave you with some Saint Seiya OST. Under the wood of the world tree:www.youtube.com/watch?v=ZcApmS…
Let's see if this one becomes popular.