How To Train Your Dragon 2

In order to unlock Stoick you first need to complete the Mouth on Fire challenge. Spread over the island there are 8 Viking Statues that you can light up with fireballs. They are located roughly at the following locations:

1. Right in the main village next to the sheep pen.
2. The island that is furthest west of the map (it's on the southern half) has a gap in the middle that you can fly through which contains a Viking Statue.
3. Just northeast of the second tournament, near the rock with a huge hole in it about halfway up the southern mountain where the grass starts becoming covered in snow.
4. On top of the smaller peak just west of the large northern mountain peak.
5. In the water just northeast of the third tournament near the northern tip of the island.
6. On a small island at the northeast part of the map (about halfway between the third and fourth tournaments).
7. In between the two mountains near the bottom on the eastern portion of the map (west and a little south of the fourth tournament).
8. On the second level of the cave that is accessible from the hole near the water level on the southeastern part of the map.

Once you’ve lit up all 8 of the statues, you can find Stoick and Skullcrusher just past the eighth statue inside the cave. Approach him with your dragon and you’ll unlock this trophy as well as adding Stoick/Skullcrusher as a flyable character in your hangar.