A royal waybill is an item in Evony TKR (The King's Return).
The description of Royal Waybill in Evony TKR says:
Use it to mail one of your items to another player.
Royal Waybill is known to potentially be obtainable from opening Lucky Box Ⅵ and Medium Hydra Chest. The links for each item are below:
Note: This list may be incomplete.