Ancient Shard

Ancient Shard is a currency item. A full stack will be combined into an Ancient Orb.

Item acquisition

Can drop from Harbingers.

Ancient Shard drops from Harbinger, which is not yet added to core mechanic. However, using Ominous Arrival atlas passive, Harbinger can be spawned in Valdo's Rest atlas region. Harbinger can also appears in Delve, from Zana crafted map mod, from map that used along with Harbinger Scarab, etc.

Ancient Shard can also drop from heist chest. Either the Currency chest or the Harbinger chest can drop Ancient Shards.

There may be additional former league mechanic that also drops Harbinger currencies, but not yet confirmed, such as Blight and Legion.