Dragon Quest Monsters: Joker 2

Where can i find Estark?

I know i have to beat him in under 8 turns but where is he?

You need to have beaten the game after that, head to Cragravation and use Zip. You should see a cave on the map right next to you. Enter the cave and you'll find him. Tell him that you don't wanna slay him and that you want to prove your power. Beat him in less than 10 rounds and he's all yours.

tips how to beat him (and fierymimiga is right its 10 turns not 8)
-choose a main monster with average def and high attack gain (or synth monster with high atk with monster you want to use)
-use a HEALER: best for this are the practicly invinsible monsters cuz they mostly survive till last of your team (so they can zing) I use metal king slime (you get him for free if you've owned 150 different monsters) give him good healskill (best is omniheal, but megaheal will do for this battle)
-use oomph: if you can manage to do like 900-1100 damage each turn you can beat him with ease

Yea , Beat the game. Train to atleast lv. 60-70 Because Estark has 8,000 HP....So..Get alot of Buffers and Healers on your team. If you do damage atleast 900-1000 HP per turn you'll win. You need to beat him in under 10 turns for him to join your team,

You need to beat the game first and find estark in the cragravation. After that you should bring monster at 50-75 at attk stat more than 650 up and you have to beat estark at 10 turns below i scout him after i defeat him with marquis de leon with 800 attck and have 1-3 attack per turn so i defeat him quite easily.