Title says it all, use ashes and tarromin on a vial of water for a serum 207. The potion itself has no use but it does give 50 xp(on osrs), gives another training method for people who dont have limps.
It's useful but honestly for an ironman the serum really doesn't give anything useful efficiency wise, you can just craft low leveled potions to offset the gap.
Although this would makes ashes more useful, as well as having another method for low/mid lvl training, the serum doesn’t really have any useful properties. Neutral.