When a dog dies, they are granted a second life. A life without humans on a dimension close to them and yet very different.
It wasn't always like this.
They always had the chance to get reincarnated though, if they weren't ready to enter Underworld (the layer of the dead).
Once there was a stray dog called Laika, who has been abused by human kind by getting brutally trained to get shot into space, where she found her death.
When she died and was asked if she wished a reincarnation or to move to Underworld, she refused both. She said every dog coming from earth deserves a second chance without human interactions. Destiny agreed heavily and formed a new dimension. Laika was send there first. New dogs joined every day. However, many chose to enter Underworld instead or hoped to get reunited with their former humans through reincartantion.
The dogs going there formed a new body. A body mirroring their former body, in best shape.
When they enter Laika's layer, they will age, can get hurt, ill, and even die again, just like a normal living being. They can also procreate. In Underworld, they do not age, can't die and can`t breed.
So Laika's Followers, that's what every dog that joined her dimension is called, could have offsprings without any humans stealing or killing them.
In the first months, Laika's pack grew in numbers slowly. Within a couple of years, when Laika was already growing older, the territory got growded. So she sent explorers out into the world of hers to find new suitable places. Multiple packs were formed as well as territory boundaries.
There is an important crystal, in a cave called "Cave of Freedom" which keeps Laika's Layer stable and connected to all the other layers. Only if the crystal is unharmed, new dogs can enter Laika's Layer.
To protect the crystal at all costs, Laika and a few close friends, decided to form a pack, which should receive special blessings.
Once a pack member has proven themselves as worthy to be a "Protector of the Layer", they'd be granted a special feature which might be handy in battle.
These Protectors weirded the other packs out, as they had features, normal dogs would not have. So the others started to call them "The Odds" (derived from the odd ones).
Why would anyone want to harm the crystal, you might ask.
With the creation of a third choice, a continuation of the former life on another layer, which is not Underworld, Anubis, Lord of Underworld, was not pleased. Destiny had to make a deal with him, not make the life on that layer so easy.
Anubis created "The Reapers". Formed of earth and bones, their job was to bring the "cheaters" to Underworld, where they should be.
If a new Follower of Laika enters her layer, they must find a pack to live with or try to live on their own. Not every pack will accept every dog, so some might not have an easy time settling down there.