Farming Distilled Fear
In Season 7, Distilled Fear is required to Diablo 4 Items summon The Beast in the Ice. There are a few ways to farm this material:

Nightmare Dungeons: These dungeons can drop Distilled Fear, though the drop rate may vary.

Tribute of Titans in Kurast Undercity: A new source of Distilled Fear, especially through Tribute of Titans.

Tree of Whispers Caches: These caches, especially the ones related to Boss Materials, occasionally drop Distilled Fear.

The higher the World Tier in which you're farming, the better your chances are of buy Diablo IV Items receiving Mantle of Mountain's Fury, as bosses at higher tiers drop more Legendary and Unique items.