It was when I was reading BESM d20 that this idea came to me. The “Train a Cute Monster” attribute noted that, for all her tactical expertise, a monster trainer was not the one fighting. So I started to wonder about a setting where this wasn’t true. I came up with this abomination.
Not content with simply commanding the magical little (and not-so-little) monsters of their world, its sapient inhabitants chose instead to take that power for themselves. Many and varied were their methods.
Some of them made elixirs of bodily fluids, enhancing their natural abilities beyond what was naturally possible. They could move faster than sight could track them, or beat even Daredevil's mighty senses. Those who know how to craft even one such elixir are careful to protect their secret, and there are many guilds that have formed around a few choice elixir recipes.
Some of them took organs. Elixirs could grant many abilities but only temporarily; the agelessness or venom of certain monsters could be had forever with a few organ transplants. Such doctors of the macabre are like patchwork men. It is hard to mistake them for normal humans in good lighting, but then there are the rare few whose genius was with them from the beginning, who never left a single scar. Such doctors are able to walk unnoticed.
Some of them made powerful artifacts and totems from the corpses of monsters. There are monsters so bloodthirsty that their fangs always home in for the kill. There are monsters whose small, fragmented bones will gently shake whenever danger is near. They wear their power, their tough hide robes and arm-bone staves, and they do it proudly.
Some of them bound the spirits of monsters to their own. There are monsters that know things, that whisper these into the ears of those that can listen. But more than that, their strength, their tenacity, their speed can be channeled through their spirit's enslavement as easily as through any other method, if less potently. Many of them are mentally unstable. That's just how it is, binding the spirits of the dead to yourself and never, ever letting go. They figure that it's worth it.
Few people bother with taming monsters, except for purposes similar to our own (food animals, beasts of burden, etc). It's much simpler and more reliable to take a monster's power for one's own. Far too often, taming is impossible anyway.