The Ember Crucible
What to kill and where to find the goals.
Repeatable: the items to hand in drop from the targets without limits, and you can run it again and again. Go kill those mobs and the quest comes along for free.
This is an exchange chain: the reward is collected as items traded at an NPC — the shop's full stock is not laid out here.
Quest steps

Prefect Marestella asks you to explore the Blazing Swamp in search of high-quality and unusual materials. If you can get a Prismatic Flame Core, try to craft Stabilized Magical Metal in the Ember Crucible. Monsters to be hunted - Tulben, Conjurer Bat Lord, Conjurer Bat, Lava Wyrm, Hames Orc Scout, Hames Orc Footman, Hames Orc Sniper, Hames Orc Shaman, Hames Orc Overlord, Cindermire Golem, Cindereye Basilisk, Slagbound Colossus, Emberspine Lavasaur, Cinderveil Reanimator, Cindermire Warden.
Collect: Scorched Armor Scrap × 999, Magical Metal Nugget × 999, Prismatic Flame Core × 999
This quest has no goals mapped: it is a guide task, there are no mobs in it.