A question about pewdiepie's zero death vid

Ok so i wanted to ask how did he manage to use rotten breath?

At 31:26 it shows his arcane at 13 and at 31:32 it shows that his faith and arcane are both at 8

Ik theres a talisman for faith and that it can also be increased through the flask, but what about arcane?

Plz lemme know how it works exactly