The Beast in Ice boss is definitely one of the most elaborate to summon in Diablo 4. While it isn't quite as complex as Duriel—where you have to fight both Varshan and Grigoire to gather the necessary materials to summon him—this icy demon is tied to the Nightmare Dungeon activity, which brings problems of its own.
There isn't really much of a bottleneck in terms of getting materials to fight Grigoire and Varshan, but since The Beast in the Ice requires Nightmare Dungeon completions if you want to gather lots of the Distilled Fear you need, it can take a hell of a long time.
Still, if you're intent on besting the beast, here's what you need to summon The Beast in the Ice boss. Be sure to see our Diablo 4 boss loot tables if you want to know what Unique items he has a chance of dropping.
Where to find Distilled Fear
You can get Distilled Fear by completing tier 30 and above Nightmare Dungeons on Torment world tier. Since the material drops randomly on completion, you might not always get a vial. The good news, though, is that doing higher tier Nightmare Dungeons has a chance to reward you with extra Distilled Fear.
As of season four, you can now also get boss materials as a random drop from elite enemies, and Distilled Fear sometimes drops when you complete a world boss, too. You need nine Distilled Fear overall in order to summon The Beast in the Ice, but with all these extra ways of sourcing the material, the grind isn't anywhere near as bad as it used to be.
How to summon The Beast in the Ice boss
Before you can access The Beast in the Ice boss lair, you need to use that Distilled Fear to craft a special Nightmare Dungeon Sigil at the Occultist. If you open the Ancestral section, this is the first option available to craft: Glacial Fissure Nightmare Sigil.
"Why does this sigil have affixes?" you may ask. Well, the bad news is that fighting The Beast in the Ice is treated like a Nightmare Dungeon, meaning you only have three revives overall to beat it. I don't recommend attempting The Beast in the Ice until you're at least level 85. Considering the grind even a few attempts require, it's not worth trying until you have a decent chance of success.
Once you arrive at the Glacial Fissure lair dungeon near Kyovoshad, you'll have to fight through hordes of enemies to get to the boss arena entrance. Unlike the other bosses, The Beast in the Ice will drop into the middle of the arena straight away. In general, look out for his ice breath attack which creates little projectiles, and when he jumps into the air to try and squash you.
If you manage to reduce his health, he'll summon a storm which traps you in the centre of the arena with some enemies—look out for the strafing AoEs he also summons here. Make sure to slot Sapphires onto your jewellery for that extra cold resistance.
