I don't think its about life and death. It appears to be about an entity that was so lonely that he split himself in two. Seeing as they were born of the same entity they will forever have a bond and will never be truly lonely. Now he couldn't just make a copy of himself, he couldn't give half of his happiness, half of his anger, half of any single emotion to each side. So I think the wolf and the lamb are representative of how he split himself up. The lamb being along the lines of calmness, peacefulness, and the like. The wolf containing the anger, ferocity, contempt, and so on. This is evidenced by the remark "did he chase them all?" But my interpretation doesn't end there. In the teaser the wolf seems mentally young and inexperienced.
"Tell me a story"
"Why was it lonely"
He doesn't have the memories to know that this isn't just a story, but the way he came to be. Seeing as the wolf may contain all the rage and none of the peacefulness, the entity knew that having those memories would make the wolf uncontrollable and an absolute unchecked terror. So he left those memories and those experiences to the lamb. The one that will remain calm, composed, and peaceful about it's past. It doesn't seem that this was completely successful. The wolf seems to have lingering pieces of memory about being lonely. "Why was it lonely" instead of "why was HE lonely." He asks as if he means "why did it feel lonely before?" But seeing as they are split emotions, he doesn't understand just how being lonely would feel, just that the feeling once existed in his past.
I also think this entity has something to do with death, but not quite the way you're thinking. I feel like this entity is analogous of Charon, the ferryman of the dead in Greek mythology. It is not death itself.
"All things must meet this man, so they shunned him"
In regards to Greek mythology, the souls of all mortals must take take the ferry to the underworld. All souls must meet Charon. That would be one of the loneliest things anyone could ever do, and would definitely be "shunned" by all. take souls from one place to another never to see the same soul twice.
Now in the case of this entity, since the mark appears randomly upon death, it could be related to the force responsible for bringing the champions soul from the battlefield back to the fountain, And playing into the player experience. no one goes "I want to stay in this limbo where I can't do anything." Everyone wants to re spawn. They want to leave this limbo between death and re spawn, eagerly awaiting to reappear in the fountain and leave whatever force (or entity) gets them there. Effectively "shunning" the entity responsible.
Edit: I just thought of a cool ult passive for a champion like in this theory. They can grab the sole of a single dead ally. And if they can get back to the fountain (recalling or walking) without dying, they re spawn their ally instantly. Large cooldown, obviously.
