Although this was a single-player Death Game with no interference from other Realm Walkers, Yan Ao did not lower his guard.
The Death Option provided three targets for elimination and allowed a generous 144 days, which indicated that none of them would be easy to deal with.
Judging by their names, all three targets contained the word "Abyssal," and this particular realm happened to be called the "Abyssal."
Chapter 458