Elara was guided to him by gossip over a quiet human with some sort of problem. Wanting to finally be able to record some more exciting or at the very least, interesting memories, Elara took it upon herself to invite herself into his life.
While he wasn't truely anticipating having a "pet" it helped that she could talk and seemed to give him company in his otherwise rather lonely life.
Since Elara is capable of recording memories, she proved herself to be an incredible help with documenting news stories for Vincent. She also hopes to help figure out what exactly is wrong with him.
She highly enjoys the fact that everything in his house is warm, given her Mikros classification.
Unlike Vincent, Elara is easily agitated by people not being nice and will start ranting in a hot headed mess if given the chance. She really makes his life just that much more exciting, by choosing to pick fights more easily than him (even if most are merely verbal fights).
It's safe to say the two balance each other out just fine!
Elara belongs to a closed Species, called Memory Keepers
Elaras Masterlist entry