I notice a lot of people are having issues and I will put some suggestions here based on my experience in the beta. I have seen similar posts from others and perhaps they can add their own wisdom here so more people can finish the levels.
Before I start, there are some teams with a lack of attack power and/or a lack of items that will make it very difficult or impossible to finish the levels.
Hints for playing
The following strategy works to optimize your attacks, especially on levels with Guinevere.
Don’t always choose heroes for special attacks unless they do something you want. Little John or Hel decrease mana regeneration, and obviously you want to do damage but many times I would rather have a hero with high sword power vs one with a lot less attack power and specials. Melendor has an attack power of 714 even though he is a healer, and is quite useful at times.
In this challenge, each level is different and if you have extra heroes it pays to optimize your team for both the minions and bosses. It is too easy to use the same team over and over which is fine, but not the best way. Items should be optimized as well.
Get through the first two levels of the stage and have all heroes charged. A diamond or two at the end or at least a good setup is important for the next level.
On the last level, use your attacks until the heroes are powering up their special. Note that if you have a bad board and can’t make much happen, abandon ship – it isn’t worth it to use items up. That will guarantee you are only focusing on good boards.
Use axes, bombs, and/or dragon attacks to lower hit points and/or attack power of bosses. After discharging specials and some tiles, recharge your potent heroes with mana potions and hit again. If you are close to killing one of the big heroes, don’t forget to use more axes etc. Tornadoes can be of tremendous help if used here because they can give you another round of specials…but don’t waste them unless you are doing really well on the level.
Time stops do not pause three turns on these bosses. They do delete the existing mana. Use them if the specials are about to go off but don’t expect miracles
Guinevere – she is a pain in the a**. If her special goes off and you were charged, then it is fairly easy to recharge the rest of your mana using a potion. Overcome her special purple defense and regeneration with a debuff from someone like Caedmon etc. Do that before your other moves so you will get maximum benefit.
Arthur – remember that if he hits you, you will have a -54% defense and -39% attack power. An antidote can important because even if your hit points are recharged, if his next attack is on the same hero it will kill them, and your attack power is down. Also, use tile power to defeat him (with Wu Kong) if you can. Debuff his protection from special abilities because otherwise your spells bounce off of him.
Merlin – can dispel Mindless attack with antidote (or Rigard), otherwise you need to put up with it
Morgan – used to be wimpy in the beta and is now another pain in the rear. Although you can’t dispel her special, you can use items to keep healing for four turns, then the special ends. Dispel her fire resistance if you can
Lancelot – fairly straightforward