Great Ghoul

is the main opponent in the game. You will face 3 random bosses from the previous zones.
 * Phase 1 begins and a boss will be picked from zone 1,2 or 3. At the same time the Great Ghoul will summon 4 fire rocks on the screen that block you and can spew fire. You can break them, but breaking all of them will push the boss into phase 2. Defeating the 1st Phase boss is recommended.
 * Phase 2 starts either when the 4 fire spewing rocks are broken or when the 1st boss is defeated. If the 1st boss isn't defeated it will remain a threat making phase 2 harder. The 2nd boss will be chosen from zone 4 or 5 and at the same time the Great Ghoul will summon 4 lightning rod enemies that block you. Breaking 3 of them is recommended, but leaving one and killing the 2nd Phase boss is the best strategy.
 * Phase 3 starts either when the 4 lightning rods are broken or the 2nd Phase boss is defeated. Again, if the 2nd Phase boss is still alive, it will remain a threat in phase 3 increasing the difficulty. The 3rd Phase boss will be chosen from zone 6 or 7 and at the same time the Great Ghoul will summon 4 Poison rocks that block you. In this phase the Great Ghoul can frost blast one of your heroes and if they are soaked they freeze for a dangerously long time. it is recommended you break the 4 rocks as soon as possible as this will stop the freezing ability and allow you to attack the final boss and end the fight. If you can focus multiplied double attacks that hit the 20 stamina Great Ghoul boss you can kill him and ignore the 3rd phase boss. A portal spell that pulls the boss close is very useful. As the Great Ghoul is a transparent ghost, he must be soaked, poisoned, or burned in order to physically attack him. If you have a damaging dark spell on a character with a lot of remaining HP, you can try to cast it repeatedly to attack on the Great Ghoul. Once the Great Ghoul's HP is fully depleted the remaining enemies on screen will die.  It is difficult to do, but if you can destroy the 4 poison rocks before the 3rd Phase boss is summoned, The Great Ghoul 20 stamina boss will trigger and the 3rd Phase Boss will be skipped entirely, making the boss trivial.
 * Pick your character for your purple chest clear reward.