Oneiric Shards are the premium special currency in Honkai: Star Rail.

They can only be obtained through in-game purchases.

Oneiric shards can be converted to Item Stellar Jade on a one-to-one ratio. They can also be used to purchase special items in the Contract Shop.

https://honkai-star-rail.fandom.com/wiki/Oneiric_Shard
oneiric shard (honkai: star rail)