The Angelic Shard drops from Izual in Act IV, and the Blacksmith will use this item to craft the Hallowed set. The Angelic Shard also drops from Corrupted Angels which you will probably find often in the Silver Spire Level 1 while completing bounties in your group, but it is more effective and less time consuming to farm Izual solo several times until it drops.

angelic-shard-2

Source

Drops from:ActLocationPortalImage
IzualAct IVThe Great SpanThe Silver Spire Level 1izual
Corrupted AngelAct IVThe Silver Spire Level 1The Silver Spire Level 1corrupted-angel