Items, NPCs, quests, objects and spells of patch 1.12.1, read live from the realm itself.

Thunder Lizard Blood

NPC	Level	Zone	Chance
Stormhide	22 - 23	The Barrens	80.0%
Thunderhead	20 - 21	The Barrens	80.0%
Stormsnout	18 - 19	The Barrens	80.0%