It appears that developers are increasing the number of sources for Mythic Unique drops. In Season 5, they will drop from Tortured Gifts otherwise known as Helltide Chests, the Purveyor of Curiosities, and Whisper Caches from the Tree of Whispers. This comes in addition to the other known sources of Mythic Unique drops, of which all are extremely rare: from monsters in the Open World, Nightmare Dungeons, and as crafted items through the Alchemist with 
Resplendent Sparks.
On the subject of Mythic Uniques, Season 5 introduces new visual effects to make the items stand out more both when they drop and in the player’s inventory.
We’re adjusting 
Baneful Heart drop rates as they were dropping too frequently to feel valuable. Chance to get one from a Tortured Gift starts at 13%, and increases each time you fail to get one. Once you are rewarded a Baneful Heart, the chance resets to 10%. Hellborne and the Helltide Assassin starts at 1% chance to drop a Heart, and also increases each time you fail to get one. It now resets to 2%.
Tortured Gifts in Helltide no longer contain 
Murmuring Obolss.
We’ve significantly reduced the time it takes to complete Whisper bounties. We’ve now made it so that there are always enough Whispers to earn 10 Grim Favors within a given Helltide, should now take significantly less time to complete. Additionally, icons have been updated to be consistent with other Whispers. The Cull Demons Whisper Bounty now includes Fallen, Cull Fallen Whisper Bounty now replaced with Cull Cultists.
Increasing your Threat now consistently scales with the health of slain Monsters.
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