The pirate told me he would tell me his secret if I brought him back the hide of a longtooth from Skull Castle.

I have completed everything in the Castle (killed head vampire, obtained Lich staff, etc), but I have never come across anything called a longtooth.

Where can I find this creature?

Thanks.

They are running around on Skull Island and surrounding islands. Just set the spawn rate to maximum and one (or a pack) should show up. I actually got a hide b4 I got the quest, and I wasn't on skull island and got attacked by 3 longtooths. Its just luck. I think I found them on that small island thats north-east of Brimloch, right on the edge of the map in the first little area.