Board Thread:Game Discussions/@comment-68.179.41.129-20131220140005/@comment-23870891-20131224213427

The hurdles for beating bosses are lvl 15, 43, and 60. After defeating each level, subsequent defeats of it become easier. That being said, as other have pointed out your level not only influences your health and attack, but the attack and apparent health of your hires. At this point in the game you should be focusing on leveling as much as possible. Go one zone lower then your current max, use a good armor, and run a middle level difficulty it till you have no health on all your knights. Wait to recharge then do it again.

"Then I suppose I could come back and fight again to try and finish it off but it always seems to regain health or i have no more attack points."

There a a few important rules to fighting the epic boss, once you summon him by fighting minions you have a 2 hour window to defeat him. Assuming you start with full energy (10) and have some friends to hire, you choose your best line-up and hires and fight him with 5 people. This takes 3 + 2 + 1 + 1 + 1 energy for a total of 8 energy, leaving you with 2 left. Strength varies but from your comments the boss will still likely have some health left. Energy recharges at a rate of 1 every 25 minutes. Assuming you attacked the boss as soon as he appeared, then you have 119 minutes until he retreats. This means you can recover 4 energy if you wait 100 minutes. With about 19 minutes left on the clock you now have 6 energy left. Attack the boss again, either with your knights only in a (side knight/side knight/main knight) order, or using hires if you still have them (main knight/hire/hire). This should do enough damage to defeat him if your friends are good and your own knights are decent.

there are also elemental advantages to consider, but numerous other threads already discuss those.