Hirimuwi

Who is Hirimuwi
This NPC will give you Mithril Coins baby !!!

He is located in the second part of the market.

The Interface
Once you have 100x of 17 carat diamonds which can be found in the Gold Room.

Just talk to Hiwimuwi and the NPC will exchange it for a certain quantity of Mithril Coin.

Note: Mithril Coin exchange rate is 1:10mil zeny.