Leviathan

I’m currently setting up a good team and I want to know if he is good and where you can catch, thanks!

he is very good. I personally caught Levi (its pre-evolution) looking in this thread http://www.hunterislandforum.com/index.php/topic/209-the-semi-rare-arkadions/

thanks now i can get my team into a better balance of all the elements 

Leviathan is good. There are a lot of better ones, but it’s definitely a good addition to your single player team. I actually use it in my PvP team right now, but with all the new monsters I might be changing that.