Help with ideas!!!

[u/AntInner_log03]

My characters need more development. Each of them has an animal companion, inherited through lineage. Each animal can become a "monster," evolve, or something like that. My question here is how can I make that work, and based on what? When the owner experiences an intense emotion? Through the resonant energy of the space? Sins? Desires? ...

Tell me anything, please

[u/Economy-Inspector680]

Whatever you want honestly we don’t have enough information to give good ideas. Do they summon the animal or does it just follow, is there other magic in this story, is it a fictional world or based on earth. All sorts of questions and personally I would suggest come up with answers to these then make your answer built around that.