In the beginning it was just Keros. Before the void came to be Keros was a normal citizen but one day that would change. One Day keros was murdered but while Keros died, he didn't cry, didn't scream, didn't smile. He was stone faced the whole, time.
As Keros learned to accept his new fate. Burdened with keeping control of a pointless land with Chelov. Although Chelov was a lot more enthusiastic than Keros but Keros didn't care for this but for why something was coming to the void, not a lost soul, but one burning one.
Something was changing but not for the greater. The ice in the void was melting and Keros knew why Hades was on his way. Hades was the exact opposite of what Chelov wanted for Keros.
Chelov began to panic and just at that moment Hades burst through the thresh separating the void from the Earth releasing gelid wind and ice rain among the Earth freezing Sea's and wreaking havoc among the land.
As Hades ravaged the Void thrashing about stating the whole place was a mistake Keros realized his biggest flaw Hades was the one who made the mistake, he had released freezing air and ice rain onto the Earth. Keros, through Chelov, told Hades to leave. Which he did.
Later after Hades was gone. Keros filled the hole with a glacier solving the potential problem of the world freezing over. Although every now and then souls travel to the void creating vicious hail storms when entering and leaving.