The 2 biggest sources of fear for kids as they get grow toward toddlerhood are vulnerability based on a better understanding of how dependent they are on their loved ones, and an inability to fully grasp cause and effect. The former often manifests as separation anxiety and a distinct fear of anyone unfamiliar to them. The latter shows up in unexpected (and sometimes hilarious) ways, like when your kid expresses sincere terror that they might get sucked down the bath tub drain at some point. In all cases, the best thing to do is take your kid seriously and help them navigate their emotions. Encourage them to re-enact the scenarios that make them uncomfortable through play, in a context that they control. If all else fails, just buy them a really big dog.