the only thing you need to do to beat this game is to build only archers. Surround yourself with 50 or 60 archers and even the boss can't go across half of the screen..
this game is great! but i guess it's a little too easy. i passed all the epic level with the same strategy--
1) afk for like 2 minutes to wait for mana to recharge
2) roll the slow moving dogs over
3) start the invincible spell
4) move the whole troops over
5) start the invincible spell every 20 seconds until their castle breaks...
 "Paladog"){kind=icon}
 "Monster Legions"){kind=icon}
 "Incursion"){kind=icon}
 "Epic War 4"){kind=icon}
 "Epic War 3"){kind=icon}
 "Sift Heads World - Act 3"){kind=icon}