What the achievement asks
Do twelve favours for Jani, the loa of refuse, at twelve Mysterious Trashpiles across Zandalar. Five points, account-wide, both factions.
Each trashpile asks for one of two things: a short quest, or an item dropped by the creatures standing around it. Bring what it wants and Jani leaves you a treasure chest, Jani's Stash.
First, unlock Jani
The trashpiles do nothing until you have done two short introduction quests. Before that you can stand on one and it will not respond, which reads as a broken achievement.
Both factions do the same two quests, Pests then Curse of Jani, in different places:
The twelve trashpiles
Four in Zuldazar:
Four in Nazmir:
Four in Vol'dun:
Each one on video
| Task | Zone | What it wants | Video |
|---|---|---|---|
| The Great Hat Robbery | Zuldazar | a quest | Watch |
| Big Hunter Mon | Zuldazar | a quest | Watch |
| Golden Ravasaur Egg | Zuldazar | Savagemane Ravasaur | Watch |
| Feathered Viper Scale | Zuldazar | Feathered Viper | Watch |
| Taking the Loa Road | Nazmir | a quest | Watch |
| Nazwathan Relic | Nazmir | Nazwathan Guardian | Watch |
| Snapjaw Tail | Nazmir | Primal Snapjaw | Watch |
| Vilescale Pearl | Nazmir | Vilescale Guardian | Watch |
| Saurid Surprise | Vol'dun | a quest | Watch |
| Polished Ringhorn Hoof | Vol'dun | Ringhorn Strider | Watch |
| Sturdy Redrock Jaw | Vol'dun | Redrock Scavenger | Watch |
| Charged Ranishu Antennae | Vol'dun | Ranishu Ravager | Watch |
Two things that save time
The named creature is not the only source. Each item drops from the similar creatures around the trashpile, not only from the exact one named above. If the Ringhorn Striders are camped, the stags nearby drop the hoof just as well.
If the treasure chest does not appear after you deliver, it is almost certainly on respawn because someone looted it recently. Come back later and it will be there. You do not have to find the item a second time: your side of the bargain is already done.