Very first trial 

"So, basically, when trying to use the runes, knowing about the flow of mana and how to input it into my body through them isn't enough?" asked Ares. At this time, they were still on their endless journey to Goliath. Both his arms were still stabilized, and his bones were healing at a fast pace, but it was not enough yet. 

"Yes, that's what I meant. I know it's already very complicated to know these two fundamentals. After all, a Runic Artist needs to do things in a completely different way in comparison to Mystical Artists. While the latter need to perceive the flow of mana and the position of the Mana Orb inside themselves, the former needs to take the mana of each living and non-living being around. Then, the runes convert it into a type of mana that isn't too destructive to the body, but most runes are not sufficiently effective. Actually, none is."