Sadness

In his rage, Tishn charged with his full power however this time, it was easier for Severus to dodge his attacks. The black mist protected him as well as helped him veering away from attacks.

"Don't rush Tishn. It is now useless to fight. Since you are born are from the darkness, you can absorb it and go on and on while fighting but, now I am capable too, to control the darkness and the same darkness will protect me. You just can't hurt me. Not even a scratch. Try if you don't believe me"

Of course, Tishn believed in him but he was not at all going to accept the defeat, so as usual, he attacked vigorously.

To no avail.

"Told ya", Severus smiled curtly but his tone changed completely in next instant, "CHECKMATE Tishn"

The voice of Severus was too cold. 

The game came to a stalemate. No one was able to defeat other. Either they could fight for their entire life or come with up in an agreement.