So the Ancient Anvil / Agris Essence system is broken for the category:

Horse/Wagon/Donkey Gear, Matchlocks/Sniper Rifles, Fishing Rods/Floats, Mount/[Guild] Mount Equipment

From the release notes from 17/04, this category is all meant to share a single agris pool:

However, testing with my limited gear available, shows that the category is sharded into multiple separate agris pools.

They seem to be broken up both by enhance material used (black stone and Concentrated Black stone are in different pools), and the grade/colour of the gear  (Blue and green gear using the same upgrade material are also in different pools).

I notified Support on 19/04 and 24/04, trying to find out If this was an error with the release notes, and the anvil is working as intended, or if this is a bug. Support claim that this was forwarded to the developers on both occasions.

As of now, 09/06, The devs have still not answered this question, or made any acknowledgement that there is a bug present in the known issues or updated the release notes to describe how the Ancient Anvil system is actually meant to work.

Below are some screenshot series' showing how different gear from this suposedly common category, are in different pools.

(If anyone knows how to hide these spammy screenshots with spoiler tags, please let me know and ill edit)

Series 1:

01-A:  This shows a 'green horse' gear, at +7 level, enhanced using black stone. This has full agris 8/8.

01-B:  This shows a green ship gear, also at level +7, enhanced with a concentrated stone. This does not share the same pool as the horse gear in A.

01-C:  This shows a blue wagon gear, also at +7, enhanced with a concentrated stone. This also doesnt share a pool with the horse gear in A

Further testing with the green ship gear and blue wagon gear, not shown, also showed the different grade items were further in separate agris pools.

Series 2:

02-A:  shows a 'blue wagon gear' having 0 agris stored. after this screenshot i deliberately failed an enhancement pushing the agris pool to 1.

02-B:  shows a different 'blue wagon gear' item, now also having a pool of 1, showing these share the same pool.  So gears that are the same grade, and using the same enhance mat, do seem to share a common pool - So the whole category isnt separate like with accessories.

A third set of pics not shown, show that  green gear enhanced with the same material, also share a common pool.

So, it would be great if we could get some acknowledgement from the devs that this situation is occuring, and set out if its intentional - and the release notes are wrong, or if there is a bug and the ancient anvil / agris essence system doesnt work as described, for the category Horse/Wagon/Donkey Gear, Matchlocks/Sniper Rifles, Fishing Rods/Floats, Mount/[Guild] Mount Equipment.

Note that I dont have the gear to test any of the other anvil categories.  So if any other categories are behaving the same way, please post details below :)