Modern Earth. Magic does not exist here.

Seneca was the leader of a small family pack before being breached to Infinitas.

Seneca was born on the slopes of the valley of Slough Creek in Yellowstone National Park. He managed to avoid becoming lunch for marauding predators, and made it through the lean months of his first autumn.

As the little wolf grew, he followed his parents up into the mountains, and back towards the cliffs of Amethyst Mountain in pursuit of the migrating elk herds, where he followed the adults on hunting excursions, eventually learning his own way.
Poor little guy got a few solid hooves to the head for his effort, inflicting a mild limp that never fully healed.
Over winter, he followed the pack through their territory, learning in turn how to fight rival wolves and defend their territory.
Come his first birthday, his responsibility in the pack shifted to defending and watching the new young pups of the year.

After repeating the same routine as his first year, learning how to properly take care of pups, defend a territory, and work with packmates on a hunt, Seneca finally started feeling the call of the wild, and set out while the pack was in the Amethyst Mountain region.
While here, he eventually found his heart in another young wolf - a female named Yukiko.

Settling the slopes of Amethyst with an independent gal that he thought was as cute as a button, Sen and Yukiko laid down a territory, found a den, and birthed a sizable litter of seven pups.
With several scares for the lives of the little squeaking potatoes, Sen and Yukiko eventually saw them to a healthy and plump age, whereupon they set out to find a rendezvous site.

Whilst guiding his little family across the valleys towards a summer home, a thunderous red breach split open. The cautious Yukiko quickly shepherded herself and the pups away from the calamity, while Sen - practiced by months of keeping the pups safe from hungry predators - ran ahead to engage the unfamiliar threat.
He drew too close, and was ripped through the interdimensional rift, being ejected into an unfamiliar realm with quite a bit more "him" to him than he remembered.

One of the gifts granted to the wolf by the red breach was an unusual clarity of mind for a simple wolf. Seneca is now fully sapient and sentient.