Opening Whimsyshire too early in Diablo 4 could cost you its best loot
One guaranteed portal, no promise of a second, and good reasons to wait for Torment 10.
Every Diablo 4 player who reaches Season Rank 5 in the Season of Hell's Legacy will get one guaranteed trip to Whimsyshire. But only one 
Liquid Rainbow will be given. This item will open the portal and will disappear from your inventory when you drink it. Getting another is just luck based. So the real question is when should you use this item to get the most rewards?
It is probably best to wait for Torment 10 or higher, as long as your build can clear it comfortably.
What Can Drop in Whimsyshire
You should never ignore the rainbow portal, and make sure to look out for the following when entering the realm of Whimsyshire.
Happy Clouds drop runes, Soul Splinters, gems, and crafting materials when activating them. A lot of reports from players say this is a great source of runes.
Make sure to clear the whole map before heading to the boss, as it is full of extra loot containers like Candy Jars, Soup Chests, Weapon Gifts, and Armor Gifts.
Players are reporting an interesting amount of Diablo 2 runes dropping in the realm.
Neigh'relle, the unicorn boss, will guarantee the drop of the Fancy Pants title. We know this is the only fixed reward.
Why Torment 10 to 12
The game team has not confirmed that Whimsyshire's loot changes based on Torment. But the community's overall feeling is that it is best to run it at higher Torments. Players reported noticeably better loot at Torment 10 and above. Some even said that for runes and splinters dropping from the Happy Clouds, Torment 12 is the sweet spot.
This also matches the usual mechanics of Diablo 4. Torment 10 in Diablo 4 is usually where the reward curve starts to flatten, and where Mythic Horadric Seals unlock.
So there is no need to push all the way to Torment 12, especially if that difficulty is currently too high for your build. You should make sure you can run your Whimsyshire at decent speed. If you can barely survive, then the run will be wasted. Make sure to keep your Liquid Rainbow for when you can clear Torment 10 comfortably.
How to Do More Whimsyshire
- Ghost of the Cow King
The Rank 5 Liquid Rainbow is not the only way in. Whimsyshire portals also have a small chance to open after killing Treasure Goblins in Helltides, or clearing a Waking Nightmare. Baal, Mephisto, and Diablo all have a small chance to drop an extra Liquid Rainbow.
However, you can only hold one Liquid Rainbow at a time. Another one will not drop until you have used the one in your inventory.