Unlike some items tied to quests, the Ring of Diablo IV gold the Midnight Sun is a world drop unique. That means it can appear in loot pools across multiple endgame activities, though certain methods provide better chances than others:

Nightmare Dungeons
These dungeons are the most consistent way to farm unique items. The higher the tier, the richer the loot pool, making them a prime target for anyone hunting this ring.

World Bosses
Ashava, Avarice, and Duriel are known to drop unique jewelry. Since these bosses appear on predictable timers, grouping up to farm them is a reliable strategy.

Helltide Chests
In Helltide events, focus on opening Chests of Mysteries or jewelry-specific caches with Aberrant Cinders. These targeted rewards significantly increase the odds of Diablo 4 Items finding unique rings.