The Venomhide Ravasaur is a mount available to Horde players after completing many daily quests in Un'goro Crater. The NPC that will start this quest line is Mor'vek in Un'goro Crater. The first quest you will be required to do is "Toxic Tolerance" which requires you to get hit with Venomhide Poison from the Venomhide Ravasaurs in Un'goro. Best thing to do is take off your weapons and beat the Ravasaur since you can only get poisoned from attacking them.
The next quest you will be required to do is "Venomhide Eggs". This quest requires you to run around and collect 4 light colored eggs from the Venomhide Ravasaur nests. After you complete this quest Mor'vek will give you "They Grow Up So Fast". It will require you to collect the following items:
x20 Venomhide Baby Tooth
x20 Rugged Leather
The hardest part of this is the Venomhide Baby Teeth. You can only get one a day by completing the daily quest that the Venomhide Baby Raptor gives you. Below is a list of each daily quest and how to do it.
The Baby raptor wants you to kill Silithid mobs in southern Un'goro for Silithid Meat. The meat has a chance to drop from any of the Silithid mobs in this area. You will need 10 portions of meat, after you collect all 10 right click them in your inventory with the Raptor out to feed him.
Hungry, Hungry, Hatchling
The Hatchling wants you to kill Stegodons, Pterrordaxs or Diematradon's in Un'goro for their meat. You can find any of these mobs all over Un'goro, however the best place to farm them is to the far southwest in Terror Run. Once you get 15 portions of the meat, right click it in your inventory to feed the raptor.
Poached, Scrambled or Raw?
You will need to head to western Tanaris for this one and collect 12 Silithid Eggs from outside or inside the tunnels at the Noxious Lair. After you get all 12 eggs you can feed them to your raptor pet by right clicking them in your inventory.
Searing Roc Feathers
This time the Raptor isn't hungry. He wants you to collect Searing Roc Feathers for him. They can be found off the Searing Roc's in southern Tanaris. The Roc's can always be found around bones, kill them for 5 of their feathers then turn them into the raptor.
After you've collected 20 teeth and all of the other required materials return to Mor'vek and turn in your quest. He will award you with the Whistle of the Venomhide Ravasaur. Congratulations!