Artodo was brought to a halt by Sir Arryn when he threw a spear which landed on his left eye and penetrated through his head. The spear was meant for Artemis, but Artodo took it and saved his rider. Sir Arryn didn't live to tell a tale about how he managed to struck down a dragon, maybe if he did survive the singers and murmurs would have written glorifying songs for him. But Artodo made sure to end his existence by burning him to ashes, alongside his men before he fell down.
Lucky for Artemis, he landed on his feet when Artodo fell. He tried to take the spear out of his dragon's eye but it wasn't just the eye that was damaged. The spear cut through Artodo's brain and the dragon couldn't even function properly, Artemis tried hard to remove the spear.