Book 3, Mountain Range of Magical Beasts, Chapter 21 - The Foggy Gulch (part 1)

If one desired to train using the ‘Secret Dragonblood Manual’, one must rouse up the Dragonblood in one’s veins. But there were only two possible ways by which one could agitate the Dragonblood in one’s veins. The first was to reach a certain minimum level of Dragonblood density in one’s veins. The second was to drink fresh blood from a live dragon.

But drinking blood from a living dragon was very dangerous.

Dragon’s blood, even when applied topically, would cause terrible pain, to say nothing of drinking it. However, everything in the world had its equal opposite. Blueheart Grass, when paired with dragon’s blood, made for an extremely potent mixture. But Blueheart Grass was extremely rare. Linley had previously asked about the price.

A single patch of Blueheart Grass was worth tens of thousands...