Each of the end-game bosses in Diablo 4 requires its own collection of unique items, and for the Beast in Ice, you need to get your hands on some Distilled Fear. You might want to grind out some extra XP before taking this adventure on.
Where to Find Distilled Fear in Diablo 4 Season 2
You can get Distilled Fear by completing Nightmare Dungeons on Tier 30 or higher. This means you must be in World Tier IV before you can start farming the bottles of fear to summon the beast. If you manage to get a Tier 30+ sigil, the drops you need will be random. In some cases, you can earn the fear by completing the dungeon. Otherwise, you have to hope that it randomly drops from killing enemies in the Nightmare Dungeon.