Things You'll Need
Instructions
Ensure that you're ready to begin the battle between your party and the High Dragon. The only absolute is that you must have Morrigan in your party of characters. Switch to her to control her.
Hit the gong. The High Dragon will fly down from the cliff and begin to battle you. Press "A" to do a small attack on the High Dragon, which will also command your party to attack her. Shortly after, your whole party will die ... but do not worry! Go into your radial menu and into your Spells list, and assign the Winter's Grasp, Lightning and Drain Life spells to your quick-command list.
Make sure you have Quick-Heal handy on your Quick Command list. Start casting Winter's Grasp on the High Dragon. Once your party dies, the High Dragon will take flight and try to land near or next to the gong. Make sure you are not under the High Dragon when she lands. Run to the position where the High Dragon was earlier. Keep casting either Winter's Grasp or Lightning on her. The High Dragon will soon again take flight and fly back to her original position. Run back to the gong. When your health starts to get low, use either Drain Life on the High Dragon or simply Quick Heal with health potions that you have. If your Mana/Magic runs out, simply open up your radial menu and select a potion to restore it. If you do not have a Magic potion, simply avoid the High Dragon until your Magic restores itself. Lightning does three times the damage Winter's Grasp does.
Repeat Step 3 until the High Dragon is dead! If this strategy does not help you, simply do not hit the gong and complete the quest. You can always return to this area at any time and fight the High Dragon.