Schematic Reassimilation: Ambystan Darter

[item=189418] is a protoform synthesis battle pet.

To collect this schematic you need to travel to Sepulcher of the First Ones isle. After teleporting move forward until you reach waterfalls.
You could spot [npc=185312] elite if it's alive. If not - look for a column of runes. Under there is a top of a pillar above the water surface.
Face the runes / elite and carefully check the water left of them to locate the schematic. May be hard to spot it.
After bringing the schematic to Protoform Repository you will learn how to create [item=189363] pet.

Here's a screen of exact spot: https://gyazo.com/aba1783dbdf354b529ff4978de9ea818

[item=189418] location - https://youtu.be/IKrNHlsPHxw

Materials list:

• 
  
• 250 x [item=188957] - drop from mobs all around Zereth Mortis
• 
  
• 1 x [item=189160] - ?
• 
  
• 1 x [item=187635] - AH or Drop List
• 
  

/way 78.13 53.11 Schematic Ambystan Darter

To unlock protoform crafting:

Complete chapters 1,2 and 3 of Secrets of the First Ones zone campaign.
Research [order-advancement=1931] and complete [storyline=1285] questlines.
After daily reset complete The Lost Component + A New Architect quests to unlock [spell=366367].
Complete Protoform Synthesis quest to unlock [spell=366368]

To get [item=189363] you need to find [item=189418] in Zereth Mortis and bring it to the Synthesis Forge*, then collect reagents for the craft

How to get Schematic:

1. 
   
2. How to get [item=189363] video: https://youtu.be/CsR_H4LLnTg
3. 
   
4. Location map: https://i.gyazo.com/cc53d20d44c452494ce210e367875cc8.jpg
5. 
   
6. What to look for Img: https://i.gyazo.com/314498567f789f506d5a958e4d531bad.jpg
7. 
   
   
8. Inside the [object=375270] near Sepulcher of the First Ones raid
   You can see a water pool and a elite frog [npc=185312] in the middle
   Schematic is to the right of the [npc=185312] frog in the water
   /way 78.17 53.10 Schematic Ambystan Darter
9. 
   

Resources required to craft (all of them are zone related):
250x[item=188957] - drops all over the Zereth Mortis
[item=189160]
[item=187634] - Can buy on AH or farm from specific mobs (check dropped by section)

* Synthesis Forge Prerequisites to be able to see a schematic & to turn it in & craft the Pet:
Complete 3 parts of the main campaign in the Secrets of the First Ones Forming an Understanding
Complete [npc=181397] upgrade [order-advancement=1904] => [order-advancement=1932] (to craft pets) & [order-advancement=1931] (to craft mounts)
Complete Protoform Synthesis quest to craft pets / Finding Tahli questchain & After daily reset The Lost Component & A New Architect to craft mounts
More detailed info can be found here: Synthe-supersized!
/way 70.18 28.60 Servitor Interface (Mounts Forge Location)
/way 61.97 58.93 Protoform Synthesis Forge (Pets Forge Location)
Right now you will need to complete the prerequisites to interact with the forge and turn in the schematic quests

Got it, thanks to the help from the other posts. One thing to mention about getting this schematic though. The Ancient Frog, though only shows as a 60 elite, is tough! And no way to grab the schematic without aggroing him. Grabbing and running doesn't work, the frog can chase you to anywhere on the isle. I'd bring along at least one well-geared friend.