Exploit: Endless Pet Experience
 

Probably others found it already. To exploit this, you need to
1. fight against an army with a group of trolls at night.
2. have a level 5 tank, green dragon prefered.
3. have inquisitors and arch mage in your army.
4. have spells level 3 magic spring, stone skin, heal. level 1 phantom
5. pet has mana regenarator skill.
6. has decent physical resistance.

The fight goes:
1. Corner enemy archers, manipulate mele enemy to attack only your tank.
2. cast spell stone skin, magic shield, heal, mana spring on your tank. so your tank won't die, and can recover some mana.
3. don't attack your enemy, troll will absord your tank's conter attack, and heal, so your enemy's strength stay the same.
4. cast phantom on inquisitor, inquisitor will generate anger for you,
5. convert anger to mana through mana regenerators skill.
6. repeat 4 and 5 forever.

I tested it, ended the fight after 100 turns, could have fought on. got my dragon from level 29 to 32. Strange thing happened. troll lost the +1 speed and initiative at night, but not the regenerate ability