The clerk is a NPC who resides in a house in western area of the Hosidius House, south west of the Hosidius bank, marked with a icon.
The clerk can be offered donation in the form of sulphurous fertilisers, where she manages their storage. Players need at least 5% favour with the Hosidius House in order to donate sulphurous fertilisers. Each bucket of fertiliser donated grants player 0.1% of progress. In order to get 100% favour purely from donating sulphurous fertilisers, a player will need 950 buckets of them.
The clerk will take all sulphurous fertilisers in the player's possession, including the bank, which means players do not need to make multiple trips to donate, and can gain massive amounts of favour in one go.
Sulphurous fertiliser is made by using saltpetre on normal compost. Both saltpetre and compost are tradeable in the Grand Exchange. However, the sulphurous fertiliser is not.