Black robe

Black Robe is a free-to-play item on the OSRS Grand Exchange in the other category.

In-game examine text: "I can do magic better in this."

It has a Grand Exchange buy limit of 125 every four hours, a high alchemy value of 7 gp, and item ID 581.

View on OSRS Wiki

Black Robe shows an active flip setup with a margin of +230 gp and 1,338 trades over the last 24 hours.

At the buy limit of 125 every four hours, max profit per cycle is about 28.8k gp — high margin with healthy liquidity.