DARKNESS can't do any harm here due to the sheer hax his opponent has. None of his forms can hurt him, possession would easily be negated, HOSTLESS has insane night vision to negate the move "Darkness", he can move in the Novaverse, which has no time at all, can just absorb his powers back along with DARKNESS's powers, can manipulate the plot to a better extent, is far bigger, can't be reality erased, will just watch as DARKNESS accidentaly erases a worthless pocket reality, doesn't need to fear speed, can eat the void, can't be mind controlled, can negate durability negation, can destroy the creations, and the rest of his abilities are useless.
Now, the only method i can see DARKNESS saving himself with is his illusions. If he transforms ito one of HOSTLESS's loved ones, he could trick him. The scary thing though is that HOSTLESS loves nobody. Not even himself. If he dies, he embraces it. If he wins, he embraces it. He has legit nothing to be fooled by, so he can just swat DARKNESS like a fly.
Really, HOSTLESS would glare at DARKNESS, and he would be destroyed.