You can get hero shards through multiple methods, such as:

-Recruiting heroes in the hall of heroes, you get 10 hero shards if you recruit a hero you already have.
- Can be obtained after completing specific missions in the hawk watch
-Could be available as rewards in some events and ranking rewards
-Could be available in some game packs
-Some hero shards are available in Road of Heroes.
-Some hero shards are available in Jailbreak