On the run

Your name is y/n, you were abused when you were only 10 yrs old, now you are 18 and have discovered that you can shape shift into any animal you want, including fake or extincted, and all animals like you. You ran away one day after bullies followed you into the forest from school, where you felt a lust for killing them. Slenderman found you and took you to his mansion offering for you to be a proxy.