Khan's brain was on fire. Violent cries filled its every corner, and a bottomless bloodlust begged him to be unleashed, but he tried to retain a modicum of concentration to channel part of his energy into the rune above his head.
Drawing runes with no hands was easier than condensing the raging sparks into a stable and meaningful symbol. Khan had never attempted to fuse the two processes, but the situation gave him no choice.
Khan could endure his lightning bolts better than the snake since his body had evolved through his element. However, his attunement was incomplete, and the Great Old One's resilience was several levels above his. Khan would always come out worse from those clashes, so he needed something stronger.