Hero Shards are also used in the Hero Evolve feature. By spending HS you can unlock cool boots for your hero and village.
The number of Hero Shards obtained can be seen under "See More" in the "Hero" menu. You can get HS by different ways.
Heroes that can be completed with Hero Shards Edit
Renee Ven (1500 HS), Abyss Demon (1000 HS), Pan Goli (1000 HS), Pounder Of That Ass (850 HS), Blockhead (750 HS), Hydrasaur (750 HS), Dick Rider (750 HS), Dick Slayer (750 HS), Cum Mage (450 HS), Glory Priestess (550 HS), Aire Elite (400 HS), Savage Chief (200 HS), Blitz Bomber (150 HS), Great Saga (1500)