General impossible difficulty (no loss)

[squallcs12]

I'm at level 13 and has just 2 dmg spell on my hand is Flame Arrow and Poison Skull. And my army has only 1 troops - Bone Dragon (1) (Init 7, Action Point 7).
At the beginning of the battle, cast Flame Arrow or Poison Skull to the highest HP enemy troop, then let my Bone Dragon wait - make sure it has highest init also. Then after enemy move, Bone Dragon fly to near the enemy troops, using ability Poison Cloud to dmg all nearby enemy. Then the next turn, move my Bone Dragon to a cell that can not be attacked by any troops and wait for Poison Cloud reload. Repeat this until defeat all enemy troops.
Each battle take much time than usual (about 50 - 70 turn) but I win for sure without loss. If combat with a enemy heroes, make sure that hero doesn't use any dmg spell like Flame Arrow or Ice Snake...etc.
I travel to all reachable islands and pick anything like gold + spell scroll + treasures ... without fight with any enemy. After that, begin fight with the weakest enemy and go on to win the game.