Before you face the dragon, try to aggro as many minions as possible over to the left and take them out by themselves.
Potions restore 30% of your total hit points. Calculate 70% of your HP and use a potion when you drop below that point. If your defense is such that you can take one hit from the dragon but not two this will keep you in the fight longer.
The most dangerous attack in the Dark Dragon's arsenal is its fire breath, an area attack that hits multiple times for huge elemental damage. You have a few tactics to take.
- Put more levels into your neck and ring slot items, as your armor and helm don't apply against it.
- If your movement bonus is high enough, always run after the dragon and get behind it, as it won't turn around to track you.
- A high dodge bonus can help avoid one or two hits if you mis-time avoiding the attack, but can't be counted upon.
- If you've been grinding for gold you've probably gained some levels by now. If the items you can buy in the store are 3-4 levels higher than the highest you can drop they'll get you through the dragon and the first few stages of the new difficulty with more ease.
- You've probably noticed that you're immune while using special attacks on your weapon (those that have animations hitting every enemy on screen). These deal increasingly less damage than your weapon swings as you gain higher levels, but offer a couple seconds where the fire breath will not hurt you. This will waste a second or two where you could have been attacking for more damage, but unless you're going for a speed run it's a good trade-off.
- The most difficult option, but one that can be done every time, is rolling out of the way. Your window of invulnerability is very small, and the moment of delay afterward means a missed roll is usually a bad day. However, with practice, this is a key skill that will become more important every time you fight the Dark Dragon at a higher difficulty.