The most efficent place to farm Hero Shards at the begginning is in
dungeon 1 battle 12. Follow the main path to the 10th battle then take the path that heads south then west. This will put you on a skull rated dungeon with a chance at earning 3 hero shards. This is the only battle in dungeon 1 that you can earn 3 hero shards.
http://loki407.xomba.com/how-get-her...y-castle-clash