Stony

After you have upgraded the mirror transportation system three times as a Venthyr, you will get the possibility to repair three mirrors a day using a [item=181363] which you will be able to buy from [npc=166133] for 20 [currency=1820]after you have completed the quick and easy quest given to you by [npc=167160] after having completed the upgrade. This will lead to this pet.

The three mirrors are not marked on the map, but they come as four distinct groups and you just need to find out which set is up on a given day and then go repair them. After a mirror has been repaired, you can go through it and hopefully, there is a chest on the other side that you can loot. Rinse and repeat.

The sets are:
Set #1
/way #1525 29.49, 37.26 Mirror, Room with Cooking Pot
/way #1525 27.15, 21.63 Mirror, Room with Elite Spider
/way #1525 40.41, 73.34 Mirror, Inside House with Sleeping Wildlife

Set #2
/way #1525 39.09, 52.18 Mirror, Room on Ground Floor
/way #1525 58.80, 67.80 Mirror, Inside House with Stonevigil
/way #1525 70.97, 43.63 Mirror, Room with Disciples

Set #3
/way #1525 72.60, 43.65 Mirror, Inside Crypt with Disciples
/way #1525 40.30, 77.16 Mirror, Inside House with Wildlife
/way #1525 77.17, 65.43 Mirror, Inside House with several Elite Mobs

Set #4
/way #1525 29.60, 25.89 Mirror, Room with Elite Soulbender
/way #1525 20.75, 54.26 Mirror, Inside Villa at Entrance
/way #1525 55.12, 35.67 Mirror, Inside Crypt with Nobles (Redelav Hall)

It is probably easiest to check these three places in South-west Revendreth to see which set is up:

/way #1525 40.41, 73.34 Mirror, Inside House with Sleeping Wildlife (set #1)
/way #1525 39.09, 52.18 Mirror, Room on Ground Floor (set #2)
/way #1525 40.30, 77.16 Mirror, Inside House with Wildlife (set #3)
/way #1525 20.75, 54.26 Mirror, Inside Villa at Entrance (set #4)

Got him today from the mirror behind the cookingpot! you need rank 3 venthyr mirror network to get him from one of the broken mirrors, there are currently 3 known broken mirrors and u can only enter them once per day. at my time of posting this the community has had access to the mirrors for 3 days.

finally some SL pet which can be sold for good money (I sold mine second for 90K on second try) because its pretty hard to get him and unlike rep. pets this one will keep its value during the entire expansion.I don't think many ppl will continue repairing mirrors after they get complete set and mount.