The Red Dragon Rune is the power of the fiery breath of dragons guarded by the Red Dragon Charlock which will be bestowed to those brave enough to duel the best.
Normal: Deals 50 points of mana damage
Upgraded: Deals 70 points of mana damage
WARNING: Spoilers below!
You can challenge him by taking the dragon adventure and earning the portal , freezing , ice arrow , and protection runes afterwords you will need to find the dragon painting which will show the symbols you have to point your wand at to enter the layer. after wards Charlock will challenge you to a duel which will you will use the runes listed above (minus portal) to drain him of his life.