I love the Depths. The darkness and the comparatively alien environment worked really well together. Gradually lighting up the place as I explored was a really fun sense of progression. It also scratches the itch of exploring and filling in a big map piece by piece AND the itch of making lots of different numbers go up (zonaite, poes, lightroots, crystalized charges, etc). My brain likes both of these things a lot. The lore surrounding it also fascinates me, as it's very likely purgatory as a real place in the world. Also the way a Bargainer statue could momentarily hijack a Goddess statue during the Great Plateau quest has really, really intriguing implications. There's just a lot about it that I find neat. Just kinda wish there were more freaky alien things down there that were out to get you. The way Froxes were described as "you only see a sparkle of ore in the darkness and then you die" was cool. I wanted more stuff like that unique to the Depths. That's about my only real complaint with them.