Hi there. The quest comes from an item that you get out of a strongbox, which can be earned by engaging in most forms of queued pvp. I recommend a skirmish win, as the drop rate appears to be very high.
You can also purchase one from the honor vendor for 5,000 honor.
Do the campaign questline until you unlock the new world quests. Then do the weekly Epic BG quest to earn 1500 honor. Open the Epic chest from the quest to get a spark fragment and your 450 trophy. Then go back to that quest hub in the new cave. Log out and back in. Look for the blood elf female that lets you exchange 1 spark fragment for 2. The only bad thing is people are upselling precog embellish atm for insane amounts like 30 - 50k and PVPers are generally broke.
You’d have to know what stat allocations are on every piece of gear that are going to be on the s2 conquest vendor to properly plan out which gear slot you want to craft a 450 piece with embellish. I didn’t see the conquest vendor on PTR so I don’t know how you are supposed to do that though.