Trouble in Hiyasan
Some items have maintenance costs. If these costs are not paid and/or the character does not have ready access to materials to perform the maintenance, then, once at any point in the day, the DM may decide to have the player roll a Wisdom saving throw for that item:
DC = 8 + 1 for every day the item has not been maintained
Failure means that the item gains the unmaintained tag. Unmaintained weapons do not add their proficiency bonus to their attack roll. If the character is not proficient in the item to begin with, then the attack is instead made at a disadvantage.
Maintenance costs are not cumulative as long as the item does not have the unmaintained tag. For example, the maintenance cost of a pistol is 3 sp. If a character does not pay the maintenance cost for 5 days, and then pays it on the 6th, the character pays only 3 sp
(and not 15 sp.)
Conversely, the DM may elect to not exercise the maintenance saving throw on any given day. Feel free to use it only when dramatically appropriate. In the above example, the DM may elect to not call for a saving throw on days 1 – 4. Before using the pistol on combat during day 5, however, the DM calls for one. the DC for this first maintenance saving throw is 13 (8 + 5).
Sometimes, even an item that is well-maintained can gain the unmaintained tag under specific conditions. Some scenarios include, but is not limited to, a firearm being exposed to rain, or a character diving underwater with a firearm in tow, etc. It is advised that an appropriate saving throw be made to avoid gaining the unmaintained tag.
Removing the unmaintained tag
The costs for removing the unmaintained tag is significantly higher than the cost for daily maintenance, but is typically not greater than the original price of the item. (That is, the actual cost is upon the DM’s discretion.)