Incorrect formula[edit source]
I added this to the Talk: Small hydra lamp page, though I probably should have posted it here:
I'm pretty sure the hydra lamp XP formulae and tables are incorrect on this wiki. I have 33 Invention, used a Small hydra lamp on Invention and Herblore, and received 8156 invention exp, using approximately 4000 invention bonus xp in the process. I will try to gain further insight on the lamp.