Hi , I am new here and a little bit late to start, but totally motivated for the challenge.
I will go to the fantasy side, and my idea is a stag viking warrior.
Quick story
Beast warrior are well known in the Norse mythology, they were Berserker (Bear), Ulfhednar (wolf) or Svinfylking (wild boar).
But coming from much older time, sagas talked about others beast warrior, taking the path of the Stag. Unlike Berserkers and other beast warrior who were subject to frenzy, used to go to battle bare chested and only relied on there brutal strength. Whose Stag warrior named Hjortrekkr, were more strategic warrior. Beside the strength given by the spirit of the stag they are mainly known for their stamina. Tales of Hjortrekkr standing several days in battle, still fighting on the pile of corpse of his enemy fallen by his axe, are not rare. Blessed by the godess Freya, whose who didn't fall in battle to go to valhalla, were gifted with an surnatural long life.
It is said that the oldest of this kind have lived long enough to served more kings than we can count. Overwhelmed by the Stag, he started to grow antlers and feets changed to hoof. He then became by far the more experimented, wise and feared warrior in and outside the battle field.
Here is some reference and moodboard
And a quick and dirty concept
I will start to block out all this in Zbrush and Marvelous designer.