Hands down, the BEST collaborative world building tool I have ever seen. Your group works together to design the world in which you will play, making everyone invested in the game before you even start playing.

Angel's Citadel did a review of Arium: Create (and it's companion Arium: Discover). You can find it here: https://angelscitadel.com/2021/02/19/review-arium-create-discover/