Need help with creating a horror mod. How to make an entity that stalks?

I'm creating a horror mod based on the Wolf Man 2025 remake. I am new to MCreator, so I need help with certain things

• I want the entity to spawn in forest and snowy forest biomes.
• I want there to be only one entity, not numerous, because it'll feel like a generic mob
• I don't want the entity to attack the player at first, I want it to stalk them for days, add psychological horror, and it gets even more aggressive with each passing day.
• The Wolf Man can break down doors, climb ladders, and trees. It will have a sneak mechanic, where the player won't even realize its there.
• It will do its best to stay out of the players field of view and watch them from a distance—hiding behind trees, terrain, structures, etc. Although, the player will catch glimpses and hear noises (twigs snapping, shuffling, leaves rustling, growls, howling)