I could probably go into super-deep detail from Weismart's blog

However, a lot of angels shepherding the spirits of the deceased to where they belong in the Shadowlands is pretty much exactly what I expected from at least one of the covenants in WOW Classic TBC Gold Shadowlands, so what pulled me was which characters were chosen to exemplify the covenant's purpose.

Blizzard based the introduction to the Kyrian covenant around Uther the Lightbringer, who is among the most significant characters in all of Warcraft.

From the animation, Uther's soul arrives on the doorstep of the Kyrian in Bastion, since there's some kind of afterlife sorting system which places souls where they belong in the Shadowlands. However, Uther can't forego his life, and he thirsts for justice. He is chastised for it for a while before Devos, the Paragon watching over him, finds that his soul is injured from Frostmourne, the Lich King's blade

I could probably go into super-deep detail about why some of the matters, but I will save myself the effort, and also you the agony of digging through it. And, Arthas, who has caused so much harm, by cheap WOW TBC Classic Gold apparently directing the ability of this maw, was throw into this evil place by the spirit of his youth teacher who expired with his own blade.