Below is the location of every wrath shard and core in the game. They're really easy to find aslong as you're not daydreaming.

Vulgrim (for sale): 1 shard and 1 core.
Vulgrim (overlord artifact reward): No shards, 1 core.
Serpent Holes: 2 shards, no cores.
Crossroads: 1 shard, no cores.
Scalding Gallow: 2 shards, no cores.
Choking Grounds: 1 shards, no cores.
Broken Stair: No shards or cores.
Twilight Cathedral: 2 shards, 1 core.
Drowned Pass: 1 shard, no cores.
Drowned Pass to Anvil's Ford Transition: 1 shard, no cores.
Anvil's Ford: 2 shards, no cores.
The Hollows: 2 shards, no cores.
Dry Road: No shards or cores.
The Ashlands: 1 shard, no cores.
Iron Canopy: 2 shards, no cores.
The Black Throne: 1 shard, no cores.
Eden: 1 shard, no cores.

In total this offers 20 shards (equal to 5 cores) and 3 cores.