Crimson Lasher

Zone: Molten Front
Vendor: Ayla Shadowstorm
Cost: 1500 Gold

To gain access to this vendor, you’ll need to complete the Filling the Moonwell quest. This pet is cageable, so you can also purchase it off the Auction House.

Unlocking the Molten Front

The Molten Front is an instanced daily area in Mt. Hyjal that you have to unlock through completing the storyline quest chain for the zone. I’ve seen places that state you only need to complete it up until Aessina’s Miracle, at which point you get the Guardians of Hyjal Calling from the Hero’s board in your city, but that guide was created in 2011 so I’m not sure if or how it has changed. If you find that this isn’t the case, your best bet is to complete the loremaster achievement for the zone then check back with Matoclaw at the Sanctuary of Malorne. Some people have also reported that boosts might only need to go to Matoclaw at the Sanctuary of Malorne, and the quest chain needed to unlock the Molten Front will already be available. Once you complete that, Matoclaw will offer you Opening the Door. You’ll go through a short quest chain that will then unlock access to the Molten Front. Once you unlock the Molten Front, you’re looking at roughly a month of dailies to gain access to the vendors that have the pets.

Starting Quest: Opening the Door
Warcraft Pets Community Guide: Unlocking the Molten Front Vendors