The Cross Reality: How To Train Your Dragon 2

Welcome To Book 2
Samantha is pushed through multiple different realities by an ungodly being, he allows her to get comfortable with someone in one reality and settle down, then he pushes them to anew reality before scrambling her memories and making her forget and restart.

Samantha Kari, or Sammy is Hiccup's "girlfriend" one could say, they do everything together eat, train, and flying out into the archipelago. What happens when a new threat turns up and almost losing her dragon.