Direct answer: the Ash of War you are looking for is called Sacred Order, not “Golden Order.” Its full skill description reads “Skill of the Golden Order fundamentalist knights,” which is where the confusion comes from. There is no item in the game called Golden Order. Sacred Order drops from a Teardrop Scarab in north-western Altus Plateau, on the road running north-west from the Abandoned Coffin Site of Grace toward the Perfumer’s Ruins.
Getting there
The Abandoned Coffin grace is the first thing you reach on the plateau if you come up through the Ruin-Strewn Precipice mines, and it is also the arrival point for the Grand Lift of Dectus. From there, take the road that follows the shore of the small lake heading north-west. The scarab is not hidden. It is sitting in plain sight on the road, and it does not move, disguise itself, or flee when you approach.
If you have already activated the grace, ride rather than walk. It is a short trip and there is nothing on this stretch worth fighting, which makes it a good one to clear while you are still hauling a half-finished weapon loadout.
How to actually get it
Kill the scarab. That is the whole mechanic. Teardrop Scarabs in this game do not flee and do not require any stealth or puzzle. Hit it once and the Ash of War pops out.
Every Ash of War can be duplicated later at Smithing Master Hewg in the Roundtable Hold using Lost Ashes of War, so there is no rush to come back for a second one. This particular ash is a guaranteed drop rather than a random one, so if the scarab is gone from your world, something is unusual.
What it does and whether you want it
Sacred Order grants the Sacred affinity and the Sacred Order skill: a salute that imbues your weapon with holy essence. It costs 18 FP per cast and is not chargeable.
The skill has one specific strength that most holy buffs lack — it is highly effective against Those Who Live in Death, and it stops skeletons from reviving after you kill them. If your build is struggling with the undead-heavy stretches, this is the ash that solves that problem rather than the generic holy buff.
It applies to all melee weapons and thrusting shields, and combines with Standard and Sacred by default. Heavy, Keen and Quality need the Iron Whetblade, and Lightning needs the Sanctified Whetblade.
One honest caveat: Shared Order is the ash most players end up preferring, because it lasts noticeably longer for only 2 extra FP. Sacred Order lasts around 30 seconds at 18 FP, Shared Order around 45 seconds at 20 FP. Shared Order is also not a Scarab drop, which is worth knowing before you commit to a weapon around either one. Sacred Order is the better answer specifically when skeleton revival is the problem, and the worse answer for general use.
Evidence status
Research-reviewed. The location, the item name, the affinity, the FP cost, and the weapon compatibility list were each cross-checked against multiple independent references. This guide has not been play-tested on camera, so treat the route as accurate but the timing of your own run as unverified.