Located in Shadra'Alor, The Hinterlands. Shadra spawns during quest Shadra the Venom Queen / Shadra the Venom Queen. She can be very difficult to tame at high level, as spawning NPCs will steal aggro and you can't attack her as she will die with one hit. It is possible, however: instead of accepting the quest from your faction NPC, go to the altar at the high point on the pond shore and accept the quest there. Immediately start taming Shadra the second she spawns and try to complete the tame before the faction NPCs run out and steal aggro. If it doesn't work, abandon the quest, re-accept and try again.