Cave of Trials 3
Enemy Hero: Kentaro The God Fist
Enemy Level: 4,500
Hero Stats: 1,320,000 HP / 38,500 Att / 4,400 Def
Aptitude: 0 / 0 / 0
Boss Spells: Special Attack, Thunder Shield
BP Cost: 2,000 BP.
Exp Reward: 30,000 Exp.
Item Reward: Giant's Foot
Strategy: Don't get hit by his attacks, you will die o.o That out of the way, read on.
This can be beaten easily by Holy Angel Seraphiel around level 1500. (I had 11060 attack on Seraphiel when I did this) 6 Angel Slayers should do. Fly 2 full teleport lengths (any farther will make you fly right into his shield) and hit him and his wargs(make sure you kill all wargs) with Ice Blaster II then fly away quick.(I used ninjas in between Ice Blaster II... They didn't do much but sending something else might make him send something else, which would throw everything off.) He will use his special attack at this point the second he finishes fly up to him quick, hit him with Ice Blaster II, then fly away. Repeat this and he should be dead before your 10 minutes is up. Watch out for when he has enough mana to use his electric shield cause he will use it and it will instantly kill you if you are close to him. If at any point you are running low on health heal yourself and if at any point his units start to build up kill them with Ice Blaster II. Note: I recommend fighting him in x1 speed cause you have just enough time to fly up to him and IB2 him and fly away quick which can sometimes be hard to do correctly in x2 speed.
Don't have/can't get Seraphiel? I beat it with Sir Kholai and used use 3 Dragon Steak Barbeques and 3 Faatality Drinks at level 2000.(I would recommend waiting until you are a higher level unless you really need the achievement for beating this.) You gotta walk up just far enough so that the farthest bolt of your Thunder III will hit him then walk away quick. I used ninjas in between each Thunder III. this will require practice and perfect timing and maybe even a little luck.
If you are still having problems with any of the strategies then I recommend leveling up a few hundred times and trying again..