The promise made to Eldrin, the dragon that had just died, was that if he killed Klaus, he would be allowed access to the Thunder Pool, which sits atop the tenth level of the Thunder Domain.
It's a vast pool of water made purely from tribulation rune energy. A single gulp can go a long way for anyone, regardless of their cultivation base.
Of course, there are different grades of tribulation pools. However, one sitting on the tenth level of the Thunder Domain wasn't something that could be underestimated.
But like all things in the heavens, nothing is given for free, so the rule was that the one who survives the 9th level of the thunder domain gets to use the pool for an hour.
Unfortunately for both Eldrin and the Heavens, Klaus was the one who won, meaning he had secured an hour inside the pool.
This doesn't look good for them.
Why?
Because Eldrin was one of the most powerful beings out there, they had expected him to succeed.
